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-0.0954 0.0462 0.0222 0.0165 0.0322 0.0373 -0.0082 0.1080 0.0865 -0.0120 -0.1003 0.0752 0.0463 Fund Performance* * Effective May 1, 2020, the Fund’s principal investment strategies were revised. 0.0995 0.1203 -0.0792 0.2423 0.1627 -0.0107 -0.2634 0.1239 -0.0100 Fund Performance* * Effective May 1, 2020, the Fund’s principal investment strategies were revised. 0.1561 0.0792 0.0614 -0.1301 0.1298 0.0770 -0.1632 0.0859 0.0202 0.0039 0.0568 0.0120 0.0129 0.0183 0.0342 0.0204 -0.0002 0.0014 0.0553 0.0387 -0.0127 0.0929 0.0875 -0.0182 -0.1355 0.0534 0.0093 2025-02-24 N-1A FLEXSHARES TRUST 2025-03-01 2025-03-01 FlexShares® US Quality Low Volatility Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Northern Trust Quality Low Volatility IndexSM (the “Underlying Index”).</div> Fees and Expenses of the Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0008 0.0000 0.0001 0.0009 -0.0001 0.0008 “Management Fees” have been restated to reflect current fees. March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">then sell all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 8 28 50 114 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 48% of the average value of its portfolio. 0.48 Principal Investment Strategies <div style="margin-top: 6pt;">The Underlying Index is designed to construct a high quality universe of companies, that in aggregate, possess lower overall absolute volatility characteristics relative to the Northern Trust 1250 Index (the “Parent Index”), a float-adjusted market capitalization weighted index of U.S. domiciled large- and mid-capitalization companies. The Underlying Index places an emphasis on a company’s income and capital growth, while also reducing overall volatility of returns relative to the Parent Index. </div> <div style="margin-top: 6pt;">To derive the Underlying Index, NTI, acting in its capacity as the index provider (the “Index Provider”) ranks all constituents of the Parent Index using a Northern Trust proprietary quality factor. This factor is a quantitative ranking based on: (a) management efficiency (e.g., corporate finance activities); (b) profitability (e.g., reliability and sustainability of financial performance); and (c) cash flow (e.g., cash flow generation). The Index Provider then excludes the lowest quintile of constituents ranked according to the quality factor and uses an optimization process to select and weight eligible securities in order to (a) seek </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">to reduce overall portfolio volatility and (b) maximize the overall quality factor relative to the Parent Index. The optimization also includes sector, industry group, style factor, single-security weight, historical beta (i.e., market sensitivity, relative to the Parent Index), liquidity and turnover constraints so that these characteristics of the Underlying Index vary within acceptable bands relative to the Parent Index. </div> <div style="margin-top: 6pt;">As of December 31, 2024, the Underlying Index was comprised of 113 constituent securities with market capitalizations ranging from $2.5 billion to $3.8 trillion. The Underlying Index is reconstituted quarterly. The Fund generally reconstitutes its portfolio in accordance with the Underlying Index. </div> <div style="margin-top: 6pt;"> NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. </div> <div style="margin-top: 6pt;">NTI uses a representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div> <div style="margin-top: 6pt;">Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts and options on futures contracts, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div> <div style="margin-top: 6pt;">The Underlying Index is created and sponsored by NTI, as the Index Provider. NTI also serves as the investment adviser to the Fund. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received). </div> <div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. Principal Risks <div style="margin-top: 6pt;">Equity Securities Risk is the risk that the values of the equity securities owned by the Fund may be more volatile and underperform other asset classes and the general securities markets.</div> <div style="margin-top: 6pt;">Low Volatility Risk is the risk that although the Underlying Index is designed to have overall volatility that is lower than that of the Parent Index, there is no guarantee it will be successful. Securities or other assets in the Fund’s portfolio may be subject to price volatility and the prices may not be any less volatile than the market as a whole and could be more volatile. The market prices of the securities or other assets in the Fund’s portfolio may fluctuate, sometimes rapidly and unpredictably. The Fund will continue to seek to track the Underlying Index even if the Underlying Index does not have lower overall volatility than the Parent Index. There is also the risk that the Fund may experience volatility greater than that of the Parent Index as a result of tracking error. A portfolio of securities with greater volatility is generally considered to have a higher risk profile than a portfolio with lower volatility.</div> <div style="margin-top: 6pt;">Quality Factor Risk is the risk that the past performance of companies that have exhibited quality characteristics does not continue or the returns on securities issued by such </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">companies may be less than returns from other styles of investing or the overall stock market. There may be periods when quality investing is out of favor and during which time the Fund's performance may suffer.</div> <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> <div style="margin-top: 6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase. </div> <div style="margin-top: 6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Underlying Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="margin-top: 6pt;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underly</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">ing Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund’s holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.•Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies. <div style="margin-top: 6pt;">Mid Cap Stock Risk is the risk that stocks of mid-sized companies may be subject to more abrupt or erratic market movements than stocks of larger, more established companies, and may lack sufficient market liquidity. Mid-sized companies may have limited product lines or financial resources, and may be dependent upon a particular niche of the market, or may be dependent upon a small or inexperienced management group. Securities of smaller companies may trade less frequently and in lower volume than the securities of larger companies, which could lead to higher transaction costs. Generally the smaller the company size, the greater the risk.</div> <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the period shown in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (6/30/2020): 15.80% </div> <div style="margin-top: 6pt;">Worst Quarter (3/31/2020): -18.55% </div> Best Quarter 2020-06-30 0.1580 Worst Quarter 2020-03-31 -0.1855 Average Annual Total Returns (for the periods ended December 31, 2024) 0.1813 0.1081 0.1105 2019-07-15 0.1766 0.1041 0.1065 0.1106 0.0853 0.0876 0.2451 0.1427 0.1456 0.1833 0.1102 0.1130 Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retire</div><div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">ment plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® Developed Markets ex-US Quality Low Volatility Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Northern Trust Developed Markets ex-US Quality Low Volatility IndexSM (the “Underlying Index”).</div> Fees and Expenses of the Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0012 0.0000 0.0002 0.0014 -0.0002 0.0012 “Management Fees” have been restated to reflect current fees. March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">then sell all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 12 43 77 177 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 46% of the average value of its portfolio. 0.46 Principal Investment Strategies <div style="margin-top: 6pt;">The Underlying index is designed to construct a high quality universe of companies, that in aggregate, possess lower overall absolute volatility characteristics relative to an eligible developed market universe, excluding the U.S. (the “Eligible Universe”). The Eligible Universe is a subset of the Northern Trust Global Index, where eligible securities are limited to those domiciled in non-U.S. developed market countries and designated as large- and mid-capitalization companies by NTI, acting in its capacity as the index provider (the “Index Provider”). The Underlying Index places an emphasis on a company’s income and capital growth, while also reducing overall volatility of returns relative to the Eligible Universe. </div> <div style="margin-top: 6pt;">To derive the Underlying Index, the Index Provider ranks all constituents of the Eligible Universe using a Northern Trust proprietary quality factor. This factor is a quantitative ranking based on: (a) management efficiency (e.g., corporate finance activities); (b) profitability (e.g., reliability and sustainability of financial performance); and (c) cash flow (e.g., cash flow generation). The Index Provider then excludes the lowest quintile of constituents ranked according to the quality factor and uses an optimization process </div> <div style="line-height: 12.10pt; margin-top: 0.00pt; text-align: left;">to select and weight eligible securities in order to (a) seek to reduce overall portfolio volatility and (b) maximize the overall quality factor relative to the Eligible Universe. The optimization also includes sector, industry, country, region, region sector, style factor, single-security weight, historical beta (i.e., market sensitivity, relative to the Eligible Universe), liquidity and turnover constraints so that these characteristics of the Underlying Index vary within acceptable bands relative to the Eligible Universe. </div> <div style="margin-top: 6pt;">As of December 31, 2024, the Underlying Index was comprised of 157 constituent securities with market capitalizations ranging from $5.3 billion to $483.8 billion. The Underlying Index is reconstituted quarterly. The Fund generally reconstitutes its portfolio in accordance with the Underlying Index. </div> <div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. </div> <div style="margin-top: 6pt;">NTI uses a representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div> <div style="margin-top: 6pt;">Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index and in American Depositary Receipts (“ADRs”) and Global Depositary Receipts (“GDRs”) (collectively “Depositary Receipts”) based on the securities in the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts, options on futures contracts and forward currency contracts, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div> <div style="margin-top: 6pt;">The Underlying Index is created and sponsored by NTI, as the Index Provider. NTI also serves as the investment adviser to the Fund. The Index Provider determines the </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div> <div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received). </div> <div style="margin-top: 6pt;">From time to time the Fund may focus its investments (i.e., invest more than 15% of its total assets) in one or more particular countries or geographic regions. As of December 31, 2024, the Fund focused its investments in Japan.</div> <div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. Principal Risks <div style="margin-top: 6pt;">Equity Securities Risk is the risk that the values of the equity securities owned by the Fund may be more volatile and underperform other asset classes and the general securities markets.</div> <div style="margin-top: 6pt;">Depositary Receipts Risk Foreign securities may trade in the form of depositary receipts. In addition to investment risks associated with the underlying issuer, depositary receipts may expose the Fund to additional risks associated with non-uniform terms that apply to depositary receipt programs, including credit exposure to the depository bank and to the sponsors and other parties with whom the depository bank establishes the programs, currency, political, economic, market risks and the risks of an illiquid market for depositary receipts. Depositary receipts are generally </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">subject to the same risks as the foreign securities that they evidence or into which they may be converted. Depositary receipts may not track the price of the underlying foreign securities on which they are based, may have limited voting rights, and may have a distribution subject to a fee charged by the depository. As a result, equity shares of the underlying issuer may trade at a discount or premium to the market price of the depositary receipts.</div> <div style="margin-top: 6pt;">Low Volatility Risk is the risk that although the Underlying Index is designed to have overall volatility that is lower than that of the Eligible Universe, there is no guarantee it will be successful. Securities or other assets in the Fund’s portfolio may be subject to price volatility and the prices may not be any less volatile than the market as a whole and could be more volatile. The market prices of the securities or other assets in the Fund’s portfolio may fluctuate, sometimes rapidly and unpredictably. The Fund will continue to seek to track the Underlying Index even if the Underlying Index does not have lower overall volatility than the Eligible Universe. There is also the risk that the Fund may experience volatility greater than that of the Eligible Universe as a result of tracking error. A portfolio of securities with greater volatility is generally considered to have a higher risk profile than a portfolio with lower volatility.</div> <div style="margin-top: 6pt;">Quality Factor Risk is the risk that the past performance of companies that have exhibited quality characteristics does not continue or the returns on securities issued by such companies may be less than returns from other styles of investing or the overall stock market. There may be periods when quality investing is out of favor and during which time the Fund's performance may suffer.</div> <div style="margin-top: 6pt;">Foreign Securities Risk is the risk that investing in foreign (non-U.S.) securities may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies, due to less liquid markets and adverse economic, political, diplomatic, financial, and regulatory factors. Foreign governments may impose limitations on foreigners’ ownership of interests in local issuers, restrictions on the ability to repatriate assets, and may also impose taxes. Any of these events could cause the value of the Fund’s investments to decline. Foreign banks, agents and securities depositories that hold the Fund’s foreign assets may be subject to little or no regulatory oversight over, or independent evaluation, </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">of their operations. Additional costs associated with investments in foreign securities may include higher custodial fees than those applicable to domestic custodial arrangements and transaction costs of foreign currency conversions. Unless the Fund has hedged its foreign currency exposure, foreign securities risk also involves the risk of negative foreign currency rate fluctuations, which may cause the value of securities denominated in such foreign currency (or other instruments through which the Fund has exposure to foreign currencies) to decline in value. Currency exchange rates may fluctuate significantly over short periods of time. Currency hedging strategies, if used, are not always successful. For instance, forward foreign currency exchange contracts, if used by the Fund, could reduce performance if there are unanticipated changes in currency exchange rates.</div> Geographic Risk is the risk that if the Fund invests a significant portion of its total assets in certain issuers within the same country or geographic region, an adverse economic, business or political development affecting that country or region may affect the value of the Fund’s investments more, and the Fund’s investments may be more volatile, than if the Fund’s investments were not so concentrated in such country or region.•Japan Investment Risk is the risk of investing in securities of Japanese issuers. The Japanese economy may be subject to considerable degrees of economic, political and social instability, which could negatively impact Japanese issuers. In recent times, Japan’s economic growth rate has remained low, and it may remain low in the future. In addition, Japan is subject to the risk of natural disasters, such as earthquakes, volcanic eruptions, typhoons and tsunamis, which could negatively affect the securities of Japanese companies held by the Fund. <div style="margin-top: 6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase. </div> <div style="margin-top: 6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Underlying Index or cause delays in the Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="margin-top: 6pt;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting. This risk may be heightened because of its investments in non-U.S. securities.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund’s holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.•Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies.•Forward Foreign Currency Contracts Risk is the risk that, if forward prices increase, a loss will occur to the extent that the agreed upon purchase price of the currency exceeds the price of the currency that was agreed to be sold. <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> <div style="margin-top: 6pt;">Mid Cap Stock Risk is the risk that stocks of mid-sized companies may be subject to more abrupt or erratic market movements than stocks of larger, more established companies, and may lack sufficient market liquidity. Mid-sized companies may have limited product lines or financial resources, and may be dependent upon a particular niche of the market, or may be dependent upon a small or inexperienced management group. Securities of smaller companies may trade less frequently and in lower volume than the securities of larger companies, which could lead to higher transaction costs. Generally the smaller the company size, the greater the risk.</div> <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the period shown in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (12/31/2022): 11.68% </div> <div style="margin-top: 6pt;">Worst Quarter (3/31/2020): -17.11% </div> Best Quarter 2022-12-31 0.1168 Worst Quarter 2020-03-31 -0.1711 Average Annual Total Returns (for the periods ended December 31, 2024) 0.0528 0.0306 0.0391 2019-07-15 0.0478 0.0254 0.0339 0.0389 0.0247 0.0314 0.0470 0.0510 0.0589 0.0553 0.0325 0.0413 Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® Emerging Markets Quality Low Volatility Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Northern Trust Emerging Markets Quality Low Volatility IndexSM (the “Underlying Index”).</div> Fees and Expenses of the Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0018 0.0000 0.0001 0.0019 -0.0001 0.0018 “Management Fees” have been restated to reflect current fees. (2) Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.18%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">then sell all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 18 60 106 242 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 96% of the average value of its portfolio. 0.96 Principal Investment Strategies <div style="margin-top: 6pt;">The Underlying Index is designed to construct a high quality universe of companies, that in aggregate, possess lower overall absolute volatility characteristics relative to an eligible emerging market universe (the “Eligible Universe”). The Eligible Universe is a subset of the Northern Trust Global Index, limited to those securities domiciled in emerging markets and designated as large- and mid-capitalization companies by NTI, acting in its capacity as the index provider (the “Index Provider”). The Underlying Index places an emphasis on a company’s income and capital growth, while also reducing overall volatility of returns relative to the Eligible Universe. </div> <div style="margin-top: 6pt;">To derive the Underlying Index, the Index Provider ranks all constituents of the Eligible Universe using a Northern Trust proprietary quality factor. This factor is a quantitative ranking based on: (a) management efficiency (e.g., corporate finance activities); (b) profitability (e.g., reliability and sustainability of financial performance); and (c) cash flow (e.g., cash flow generation). The Index Provider then excludes the lowest quintile of constituents ranked accord</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">ing to the quality factor and uses an optimization process to select and weight eligible securities in order to (a) seek to reduce overall portfolio volatility and (b) maximize the overall quality factor relative to the Eligible Universe. The optimization also includes sector, industry, country, style factor, single-security weight, historical beta (i.e., market sensitivity, relative to the Eligible Universe), liquidity and turnover constraints so that these characteristics of the Underlying Index vary within acceptable bands relative to the Eligible Universe. </div> <div style="margin-top: 6pt;">As of December 31, 2024, the Underlying Index was comprised of 153 constituent securities with market capitalizations ranging from $2.8 billion to $857.1 billion. The Underlying Index is reconstituted quarterly. The Fund generally reconstitutes its portfolio in accordance with the Underlying Index. </div> <div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. </div> <div style="margin-top: 6pt;">NTI uses a representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div> <div style="margin-top: 6pt;">Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index and in American Depositary Receipts (“ADRs”) and Global Depositary Receipts (“GDRs”) (collectively “Depositary Receipts”) based on the securities in the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts, options on futures contracts and forward currency contracts, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">The Underlying Index is created and sponsored by NTI, as the Index Provider. NTI also serves as the investment adviser to the Fund. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div> <div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received). </div> <div style="margin-top: 6pt;">From time to time the Fund may focus its investments (i.e., invest more than 15% of its total assets) in one or more particular countries or geographic regions. As of December 31, 2024, the Fund focused its investments in India, China and Taiwan.</div> <div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. Principal Risks <div style="margin-top: 6pt;">Equity Securities Risk is the risk that the values of the equity securities owned by the Fund may be more volatile and underperform other asset classes and the general securities markets.</div> <div style="margin-top: 6pt;">Mid Cap Stock Risk is the risk that stocks of mid-sized companies may be subject to more abrupt or erratic market movements than stocks of larger, more established companies, and may lack sufficient market liquidity. Mid-sized companies may have limited product lines or financial resources, and may be dependent upon a particular niche of the market, or may be dependent upon a small or inexperienced management group. Securities of smaller com</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">panies may trade less frequently and in lower volume than the securities of larger companies, which could lead to higher transaction costs. Generally the smaller the company size, the greater the risk.</div> <div style="margin-top: 6pt;">Depositary Receipts Risk Foreign securities may trade in the form of depositary receipts. In addition to investment risks associated with the underlying issuer, depositary receipts may expose the Fund to additional risks associated with non-uniform terms that apply to depositary receipt programs, including credit exposure to the depository bank and to the sponsors and other parties with whom the depository bank establishes the programs, currency, political, economic, market risks and the risks of an illiquid market for depositary receipts. Depositary receipts are generally subject to the same risks as the foreign securities that they evidence or into which they may be converted. Depositary receipts may not track the price of the underlying foreign securities on which they are based, may have limited voting rights, and may have a distribution subject to a fee charged by the depository. As a result, equity shares of the underlying issuer may trade at a discount or premium to the market price of the depositary receipts.</div> <div style="margin-top: 6pt;">Low Volatility Risk is the risk that although the Underlying Index is designed to have overall volatility that is lower than that of the Eligible Universe, there is no guarantee it will be successful. Securities or other assets in the Fund’s portfolio may be subject to price volatility and the prices may not be any less volatile than the market as a whole and could be more volatile. The market prices of the securities or other assets in the Fund’s portfolio may fluctuate, sometimes rapidly and unpredictably. The Fund will continue to seek to track the Underlying Index even if the Underlying Index does not have lower overall volatility than the Eligible Universe. There is also the risk that the Fund may experience volatility greater than that of the Eligible Universe as a result of tracking error. A portfolio of securities with greater volatility is generally considered to have a higher risk profile than a portfolio with lower volatility.</div> <div style="margin-top: 6pt;">Quality Factor Risk is the risk that the past performance of companies that have exhibited quality characteristics does not continue or the returns on securities issued by such companies may be less than returns from other styles of investing or the overall stock market. There may be periods when quality investing is out of favor and during which time the Fund's performance may suffer.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Emerging Markets Risk is the risk that emerging markets are generally subject to greater market volatility, political, social and economic instability, uncertain trading markets and more governmental limitations on foreign investments than more developed markets. In addition, companies operating in emerging markets may be subject to lower trading volumes and greater price volatility than companies in more developed markets. Emerging market economies may be based on only a few industries, may be highly vulnerable to changes in local and global trade conditions, and may suffer from extreme and volatile debt burdens or inflation rates. Companies in emerging market countries generally may be subject to less stringent regulatory, disclosure, financial reporting, accounting, auditing and recordkeeping standards than companies in more developed countries. As a result, information, including financial information, about such companies may be less available and reliable, which can impede the Fund’s ability to evaluate such companies. Securities law and the enforcement of systems of taxation in many emerging market countries may change quickly and unpredictably, and the ability to bring and enforce actions (including bankruptcy, confiscatory taxation, expropriation, nationalization of a company’s assets, restrictions on foreign ownership of local companies, restrictions on withdrawing assets from the country, protectionist measures and practices such as share blocking), or to obtain information needed to pursue or enforce such actions, may be limited. Investments in emerging market securities may be subject to additional transaction costs, delays in settlement procedures, unexpected market closures, and lack of timely information.</div> <div style="margin-top: 6pt;">Foreign Securities Risk is the risk that investing in foreign (non-U.S.) securities may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies, due to less liquid markets and adverse economic, political, diplomatic, financial, and regulatory factors. Foreign governments may impose limitations on foreigners’ ownership of interests in local issuers, restrictions on the ability to repatriate assets, and may also impose taxes. Any of these events could cause the value of the Fund’s investments to decline. Foreign banks, agents and securities depositories that hold the Fund’s foreign assets may be subject to little or no regulatory oversight over, or independent evaluation, of their operations. Additional costs associated with invest</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">ments in foreign securities may include higher custodial fees than those applicable to domestic custodial arrangements and transaction costs of foreign currency conversions. Unless the Fund has hedged its foreign currency exposure, foreign securities risk also involves the risk of negative foreign currency rate fluctuations, which may cause the value of securities denominated in such foreign currency (or other instruments through which the Fund has exposure to foreign currencies) to decline in value. Currency exchange rates may fluctuate significantly over short periods of time. Currency hedging strategies, if used, are not always successful. For instance, forward foreign currency exchange contracts, if used by the Fund, could reduce performance if there are unanticipated changes in currency exchange rates.</div> <div style="margin-top: 6pt;">Geographic Risk is the risk that if the Fund invests a significant portion of its total assets in certain issuers within the same country or geographic region, an adverse economic, business or political development affecting that country or region may affect the value of the Fund’s investments more, and the Fund’s investments may be more volatile, than if the Fund’s investments were not so concentrated in such country or region.</div> •China Investment Risk is the risk associated with investments in companies located or operating in China, such as nationalization, expropriation, or confiscation of property; alteration or discontinuation of economic reforms; and considerable degrees of economic, political and social instability. Investors in Chinese markets generally experience difficulties in obtaining information necessary for investigations into and/or litigation against Chinese companies, as well as in obtaining and/or enforcing judgements due to a lack of publicly available information; and there are generally limited legal remedies for shareholders. Internal social unrest or confrontations with other neighboring countries, including military conflicts, may disrupt economic development in China and result in a greater risk of currency fluctuations, currency convertibility, interest rate fluctuations and higher rates of inflation. Export growth continues to be a major driver of China’s rapid economic growth. As a result, a reduction in spending on Chinese products and services, the institution of additional tariffs or other trade barriers, including as a result of heightened trade tensions between China and the U.S., or a downturn in any of the economies of China’s key trading partners may have an adverse impact on the Chinese economy. Any difficulties of the Public Company Accounting Oversight Board (“PCAOB”) to inspect audit work papers and practices of PCAOB-registered accounting firms in China with respect to their audit work of U.S. reporting companies may impose significant additional risks associated with investments in China. Certain securities issued by companies located or operating in China, such as China A-shares, are subject to trading restrictions and suspensions, quota limitations and sudden changes in those limitations, and operational, clearing and settlement risks.Additionally, the Fund may gain exposure to certain companies in China through legal structures known as variable interest entities ("VIEs"), which provide exposure to Chinese companies through contractual arrangements instead of equity ownership. The China Securities Regulatory Commission ("CSRC") released new rules that permit the use of VIE structures, provided they abide by Chinese laws and register with the CSRC. The rules, however, may cause Chinese companies to undergo greater scrutiny and may make the process to create VIEs more difficult and costly. Further, while the rules and implementing guidelines do not prohibit the use of VIE structures, this does not serve as a formal endorsement either. There is a risk that the Chinese government may cease to tolerate VIEs at any time, and any guidance or further rulemaking prohibiting or restricting these structures by the Chinese government, generally or with respect to specific industries, would likely cause impacted VIE-structured holding(s) to suffer significant, detrimental, and possibly permanent losses.•India Investment Risk is the risk associated with investments in companies located or operating in India, such as political and legal uncertainty, greater government control over the economy, currency fluctuations or blockage, and the risk of nationalization or expropriation of assets, which may result in higher potential for losses. Specifically, India’s strained relations with neighboring countries like Pakistan and China could result in geopolitical risk that has an adverse impact on the Indian economy and stock market. In addition, the Reserve Bank of India (“RBI”) has imposed limits on foreign ownership of Indian securities, which may limit the amount the Fund can invest in certain types of companies. Further, certain Indian regulatory approvals, including approvals from the Securities and Exchange Board of India, the RBI, the central government and the tax authorities (to the extent that tax benefits need to be utilized), may be required before the Fund can make investments in the securities of Indian companies. Capital gains from Indian securities may be subject to local taxation. Indian regulatory or tax requirements may result in increased tracking error.•Taiwan Investment Risk is the risk of investing in securities of Taiwanese issuers. Specifically, Taiwan’s geographic proximity and history of political contention with China have resulted in ongoing tensions between the two countries, which may materially affect the Taiwanese economy and its securities market. Investments in securities of Taiwanese companies are subject to Taiwan’s heavy dependence on exports. Reductions in spending on Taiwanese products and services, labor shortages, institution of tariffs or other trade barriers, or a downturn in any of the economies of Taiwan’s key trading partners, including the United States, may have an adverse impact on the Taiwanese economy and the values of Taiwanese companies. <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase. </div> <div style="margin-top: 6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting. This risk may be heightened because of its investments in non-U.S. securities.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund’s holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.•Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies.•Forward Foreign Currency Contracts Risk is the risk that, if forward prices increase, a loss will occur to the extent that the agreed upon purchase price of the currency exceeds the price of the currency that was agreed to be sold. <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> <div style="margin-top: 6pt;">Valuation Risk is the risk that the sale price the Fund could receive for a portfolio security may differ from the Fund’s valuation of the security, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. In addition, the value of the securities in the Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarilyindicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the period shown in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (6/30/2020): 12.19% </div> <div style="margin-top: 6pt;">Worst Quarter (3/31/2020): -21.67%</div> Best Quarter 2020-06-30 0.1219 Worst Quarter 2020-03-31 -0.2167 Average Annual Total Returns (for the periods ended December 31, 2024) 0.1076 0.0200 0.0271 2019-07-15 0.1043 0.0163 0.0230 0.0741 0.0174 0.0227 0.0750 0.0170 0.0273 0.1182 0.0293 0.0359 Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® Morningstar US Market Factor Tilt Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Morningstar® US Market Factor Tilt IndexSM (the “Underlying Index”).</div> Fees and Expenses of the Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0025 0.0000 0.0001 0.0026 -0.0001 0.0025 March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 26 83 145 330 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 11% of the average value of its portfolio. 0.11 Principal Investment Strategies <div style="margin-top: 6pt;">The Morningstar® US Market Extended Factor Tilt IndexSM (the “Underlying Index”) is designed to reflect the performance of the U.S. equity market with increased exposure to size and value factors relative to the Morningstar® US Market Extended Index (the “Parent Index”), a float-adjusted market-capitalization weighted index of large-, mid- and small-capitalization companies in the U.S. A company is generally classified in the U.S. if its primary stock market activities are carried out in the U.S. and it is incorporated in the U.S. or certain U.S. territories. The Underlying Index seeks to achieve increased exposures to size and value factors, or a “factor tilt”, by adjusting the Parent Index’s constituent weights to achieve a slightly greater weight on companies with smaller market capitalizations or lower valuations, as determined by Morningstar, Inc. (the “Index Provider”) pursuant to its index methodology. The Underlying Index is designed to measure the performance of U.S. equity markets with increased exposure toward small-capitalization and value stocks. As of December 31, 2024, the Underlying Index was comprised of 2,201 issues with market capitalizations ranging from $113.2 million to $3.8 </div><div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">trillion. The Underlying Index is reconstituted on a semi-annual basis and is rebalanced quarterly. The Fund generally reconstitutes and rebalances its portfolio in accordance with the Underlying Index. </div><div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. </div><div style="margin-top: 6pt;">NTI uses a representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div><div style="margin-top: 6pt;">Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts and options on futures contracts, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div><div style="margin-top: 6pt;">The Underlying Index is sponsored by the Index Provider, an organization that is independent of the Fund and NTI. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div><div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received).</div><div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. Principal Risks <div style="margin-top: 6pt;">Equity Securities Risk is the risk that the values of the equity securities owned by the Fund may be more volatile and underperform other asset classes and the general securities markets.</div> <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> <div style="margin-top: 6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase. </div> <div style="margin-top: 6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if </div><div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Underlying Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="margin-top: 6pt;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Value Investing Risk is the risk that the Fund’s investment in companies whose securities are believed to be undervalued, relative to their underlying profitability, will not appreciate in value as anticipated.</div> <div style="margin-top: 6pt;">Mid and Small Cap Stock Risk is the risk that stocks of mid-sized and smaller companies may be more volatile than stocks of larger, more established companies, and may lack sufficient market liquidity. Mid-sized and small companies may have limited product lines or financial resources, may be dependent upon a particular niche of the </div><div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">market, or may be dependent upon a small or inexperienced management group. Smaller companies may also include micro-capitalization companies. Securities of smaller companies may trade less frequently and in lower volume than the securities of larger companies, which could lead to higher transaction costs. Generally the smaller the company size, the greater the risk.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div><div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.•Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies. <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year and (B) how the Fund’s average annual returns compare with those of a broad measure of market performance. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year and (B) how the Fund’s average annual returns compare with those of a broad measure of market performance. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the periods in the bar chart above: </div><div style="margin-top: 6pt;">Best Quarter (6/30/2020): 22.45% </div><div style="margin-top: 6pt;">Worst Quarter (3/31/2020): -26.23% </div> Best Quarter 2020-06-30 0.2245 Worst Quarter 2020-03-31 -0.2623 Average Annual Total Returns (for the periods ended December 31, 2024) 0.1993 0.1289 0.1131 0.1951 0.1243 0.1083 0.1198 0.1018 0.0921 0.2381 0.1386 0.1254 0.2030 0.1303 0.1145 In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the Morningstar® U.S. Market Factor Tilt IndexSM to the Russell 3000 Index. The Fund will continue to compare its performance to the Morningstar® U.S. Market Factor Tilt IndexSM, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® Morningstar Developed Markets ex-US Factor Tilt Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Morningstar® Developed Markets ex-US Factor Tilt IndexSM (the “Underlying Index”).</div> Fees and Expenses of the Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0039 0.0000 0.0002 0.0041 -0.0002 0.0039 March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 40 130 228 516 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 19% of the average value of its portfolio. 0.19 Principal Investment Strategies <div style="margin-top: 6pt;">The Morningstar® Developed Markets ex-US Factor Tilt IndexSM (the “Underlying Index”) is designed to reflect the performance of developed equity markets excluding the U.S. with increased exposure to size and value factors relative to the Morningstar® Developed Markets ex-US Index (the “Parent Index”), a float-adjusted market-capitalization weighted index of companies incorporated in developed market countries, excluding the U.S. The Underlying Index seeks to achieve increased exposures to size and value factors, or a “factor tilt”, by adjusting the Parent Index’s constituent weights to achieve a slightly greater weight on companies with smaller market capitalizations or lower valuations, as determined by Morningstar, Inc. (the “Index Provider”), pursuant to its index methodology. The Underlying Index is designed to include companies with enhanced risk-return characteristics relative to the broader developed international equity market by featuring size and value risk premiums, which NTI believes have been historically demonstrated over a full market cycle. As of December 31, 2024, the Underlying Index was comprised of 2,829 issues with market capitalizations ranging from </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">$302.7 million to $328.7 billion. The Underlying Index is reconstituted on a semi-annual basis and is rebalanced quarterly. The Fund generally reconstitutes and rebalances its portfolio in accordance with the Underlying Index. </div> <div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. </div> <div style="margin-top: 6pt;">NTI uses a representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div> <div style="margin-top: 6pt;">Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index and in American Depositary Receipts (“ADRs”) and Global Depositary Receipts (“GDRs”) (collectively “Depositary Receipts”) based on the securities in the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts, options on futures contracts and forward currency contracts, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div> <div style="margin-top: 6pt;">The Underlying Index is sponsored by the Index Provider, an organization that is independent of the Fund and NTI. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div> <div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received). </div> <div style="margin-top: 6pt;">From time to time the Fund may focus its investments (i.e., invest more than 15% of its total assets) in one or more particular </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">countries or geographic regions. As of December 31, 2024, the Fund focused its investments in Japan. </div> <div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. Principal Risks <div style="margin-top: 6pt;">Equity Securities Risk is the risk that the values of the equity securities owned by the Fund may be more volatile and underperform other asset classes and the general securities markets.</div> <div style="margin-top: 6pt;">Mid and Small Cap Stock Risk is the risk that stocks of mid-sized and smaller companies may be more volatile than stocks of larger, more established companies, and may lack sufficient market liquidity. Mid-sized and small companies may have limited product lines or financial resources, may be dependent upon a particular niche of the market, or may be dependent upon a small or inexperienced management group. Securities of smaller companies may trade less frequently and in lower volume than the securities of larger companies, which could lead to higher transaction costs. Generally the smaller the company size, the greater the risk.</div> <div style="margin-top: 6pt;">Foreign Securities Risk is the risk that investing in foreign (non-U.S.) securities may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies, due to less liquid markets and adverse economic, political, diplomatic, financial, and regulatory factors. Foreign governments may impose limitations on foreigners’ ownership of </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">interests in local issuers, restrictions on the ability to repatriate assets, and may also impose taxes. Any of these events could cause the value of the Fund’s investments to decline. Foreign banks, agents and securities depositories that hold the Fund’s foreign assets may be subject to little or no regulatory oversight over, or independent evaluation, of their operations. Additional costs associated with investments in foreign securities may include higher custodial fees than those applicable to domestic custodial arrangements and transaction costs of foreign currency conversions. Unless the Fund has hedged its foreign currency exposure, foreign securities risk also involves the risk of negative foreign currency rate fluctuations, which may cause the value of securities denominated in such foreign currency (or other instruments through which the Fund has exposure to foreign currencies) to decline in value. Currency exchange rates may fluctuate significantly over short periods of time. Currency hedging strategies, if used, are not always successful. For instance, forward foreign currency exchange contracts, if used by the Fund, could reduce performance if there are unanticipated changes in currency exchange rates.</div> Geographic Risk is the risk that if the Fund invests a significant portion of its total assets in certain issuers within the same country or geographic region, an adverse economic, business or political development affecting that country or region may affect the value of the Fund’s investments more, and the Fund’s investments may be more volatile, than if the Fund’s investments were not so concentrated in such country or region.•Japan Investment Risk is the risk of investing in securities of Japanese issuers. The Japanese economy may be subject to considerable degrees of economic, political and social instability, which could negatively impact Japanese issuers. In recent times, Japan’s economic growth rate has remained low, and it may remain low in the future. In addition, Japan is subject to the risk of natural disasters, such as earthquakes, volcanic eruptions, typhoons and tsunamis, which could negatively affect the securities of Japanese companies held by the Fund. <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> <div style="margin-top: 6pt;">Depositary Receipts Risk Foreign securities may trade in the form of depositary receipts. In addition to investment risks associated with the underlying issuer, depositary receipts may expose the Fund to additional risks associated with non-uniform terms that apply to depositary receipt programs, including credit exposure to the depository bank and to the sponsors and other parties with whom the depository bank establishes the programs, currency, political, economic, market risks and the risks of an illiquid market for depositary receipts. Depositary receipts are generally subject to the same risks as the foreign securities that they evidence or into which they may be converted. Depositary receipts may not track the price of the underlying foreign securities on which they are based, may have limited voting rights, and may have a distribution subject to a fee charged by the depository. As a result, equity shares of the underlying issuer may trade at a discount or premium to the market price of the depositary receipts.</div> <div style="margin-top: 6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase. </div> <div style="margin-top: 6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Underlying Index or cause delays in the Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="margin-top: 6pt;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Value Investing Risk is the risk that the Fund’s investment in companies whose securities are believed to be undervalued, relative to their underlying profitability, will not appreciate in value as anticipated.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;"> is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting. This risk may be heightened because of its investments in non-U.S. securities.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.•Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies.•Forward Foreign Currency Contracts Risk is the risk that, if forward prices increase, a loss will occur to the extent that the agreed upon purchase price of the currency exceeds the price of the currency that was agreed to be sold. <div style="margin-top: 6pt;">Valuation Risk is the risk that the sale price the Fund could receive for a portfolio security may differ from the Fund’s valuation of the security, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. In addition, the value of the securities in the Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares.</div> <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year and (B) how the Fund’s average annual returns compare with those of a broad measure of market performance. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year and (B) how the Fund’s average annual returns compare with those of a broad measure of market performance. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the periods in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (12/31/2020): 18.86% </div> <div style="margin-top: 6pt;">Worst Quarter (3/31/2020): -27.56%</div> Best Quarter 2020-12-31 0.1886 Worst Quarter 2020-03-31 -0.2756 Average Annual Total Returns (for the periods ended December 31, 2024) 0.0510 0.0454 0.0503 0.0410 0.0374 0.0426 0.0363 0.0344 0.0387 0.0470 0.0510 0.0526 0.0533 0.0461 0.0509 In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the Morningstar® Developed Markets ex-US Factor Tilt IndexSM to the MSCI World ex-USA Index. The Fund will continue to compare its performance to the Morningstar® Developed Markets ex-US Factor Tilt IndexSM, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® Morningstar Emerging Markets Factor Tilt Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Morningstar® Emerging Markets Factor Tilt IndexSM (the “Underlying Index”).</div> Fees and Expenses of the Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0057 0.0000 0.0001 0.0058 -0.0001 0.0057 March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 58 185 323 725 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 33% of the average value of its portfolio. 0.33 Principal Investment Strategies <div style="margin-top: 6pt;">The Morningstar® Emerging Markets Factor Tilt IndexSM (the “Underlying Index”) is designed to reflect the performance of emerging equity markets with increased exposure to size and value factors relative to the Morningstar® Emerging Markets Index (the “Parent Index”), a float-adjusted market-capitalization weighted index of companies incorporated in emerging-market countries. The Underlying Index seeks to achieve increased exposures to size and value factors, or a “factor tilt”, by adjusting the Parent Index’s constituent weights to achieve a slightly greater weight on companies with smaller market capitalizations or lower valuations, as determined by Morningstar, Inc. (the “Index Provider”), pursuant to its index methodology. The Underlying Index is designed to include companies with enhanced risk-return characteristics relative to the broader emerging equity market by featuring size and value risk premiums, which NTI believes have been historically demonstrated over a full market cycle. As of December 31, 2024, the Underlying Index was comprised of 3,731 issues with market capitalizations ranging from $98.9 million to $1.8 trillion. The Underlying Index is reconstituted </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">on a semi-annual basis and is rebalanced quarterly. The Fund generally reconstitutes and rebalances its portfolio in accordance with the Underlying Index. </div> <div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. </div> <div style="margin-top: 6pt;">NTI uses a representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div> <div style="margin-top: 6pt;">Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index and in American Depositary Receipts (“ADRs”) and Global Depositary Receipts (“GDRs”) (collectively “Depositary Receipts”) based on the securities in the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts, options on futures contracts and forward currency contracts, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div> <div style="margin-top: 6pt;">The Underlying Index is sponsored by the Index Provider, an organization that is independent of the Fund and NTI. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div> <div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received). </div> <div style="margin-top: 6pt;">From time to time the Fund may focus its investments (i.e., invest more than 15% of its total assets) in one or more particular </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">countries or geographic regions. As of December 31, 2024, the Fund focused its investments in China, Taiwan and India.</div> <div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. Principal Risks <div style="margin-top: 6pt;">Equity Securities Risk is the risk that the values of the equity securities owned by the Fund may be more volatile and underperform other asset classes and the general securities markets.</div> <div style="margin-top: 6pt;">Mid and Small Cap Stock Risk is the risk that stocks of mid-sized and smaller companies may be more volatile than stocks of larger, more established companies, and may lack sufficient market liquidity. Mid-sized and small companies may have limited product lines or financial resources, may be dependent upon a particular niche of the market, or may be dependent upon a small or inexperienced management group. Securities of smaller companies may trade less frequently and in lower volume than the securities of larger companies, which could lead to higher transaction costs. Generally the smaller the company size, the greater the risk.</div> <div style="margin-top: 6pt;">Emerging Markets Risk is the risk that emerging markets are generally subject to greater market volatility, political, social and economic instability, uncertain trading markets and more governmental limitations on foreign investments than more developed markets. In addition, companies operating in emerging markets may be subject to lower trading volumes and greater price volatility than companies</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;"> in more developed markets. Emerging market economies may be based on only a few industries, may be highly vulnerable to changes in local and global trade conditions, and may suffer from extreme and volatile debt burdens or inflation rates. Companies in emerging market countries generally may be subject to less stringent regulatory, disclosure, financial reporting, accounting, auditing and recordkeeping standards than companies in more developed countries. As a result, information, including financial information, about such companies may be less available and reliable, which can impede the Fund’s ability to evaluate such companies. Securities law and the enforcement of systems of taxation in many emerging market countries may change quickly and unpredictably, and the ability to bring and enforce actions (including bankruptcy, confiscatory taxation, expropriation, nationalization of a company’s assets, restrictions on foreign ownership of local companies, restrictions on withdrawing assets from the country, protectionist measures and practices such as share blocking), or to obtain information needed to pursue or enforce such actions, may be limited. Investments in emerging market securities may be subject to additional transaction costs, delays in settlement procedures, unexpected market closures, and lack of timely information.</div> <div style="margin-top: 6pt;">Foreign Securities Risk is the risk that investing in foreign (non-U.S.) securities may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies, due to less liquid markets and adverse economic, political, diplomatic, financial, and regulatory factors. Foreign governments may impose limitations on foreigners’ ownership of interests in local issuers, restrictions on the ability to repatriate assets, and may also impose taxes. Any of these events could cause the value of the Fund’s investments to decline. Foreign banks, agents and securities depositories that hold the Fund’s foreign assets may be subject to little or no regulatory oversight over, or independent evaluation, of their operations. Additional costs associated with investments in foreign securities may include higher custodial fees than those applicable to domestic custodial arrangements and transaction costs of foreign currency conversions. Unless the Fund has hedged its foreign currency exposure, foreign securities risk also involves the risk of negative foreign currency rate fluctuations, which may cause the value of securities denominated in such foreign </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">currency (or other instruments through which the Fund has exposure to foreign currencies) to decline in value. Currency exchange rates may fluctuate significantly over short periods of time. Currency hedging strategies, if used, are not always successful. For instance, forward foreign currency exchange contracts, if used by the Fund, could reduce performance if there are unanticipated changes in currency exchange rates.</div> <div style="margin-top: 6pt;">Geographic Risk is the risk that if the Fund invests a significant portion of its total assets in certain issuers within the same country or geographic region, an adverse economic, business or political development affecting that country or region may affect the value of the Fund’s investments more, and the Fund’s investments may be more volatile, than if the Fund’s investments were not so concentrated in such country or region.</div>•China Investment Risk is the risk associated with investments in companies located or operating in China, such as nationalization, expropriation, or confiscation of property; alteration or discontinuation of economic reforms; and considerable degrees of economic, political and social instability. Investors in Chinese markets generally experience difficulties in obtaining information necessary for investigations into and/or litigation against Chinese companies, as well as in obtaining and/or enforcing judgements due to a lack of publicly available information; and there are generally limited legal remedies for shareholders. Internal social unrest or confrontations with other neighboring countries, including military conflicts, may disrupt economic development in China and result in a greater risk of currency fluctuations, currency convertibility, interest rate fluctuations and higher rates of inflation. Export growth continues to be a major driver of China’s rapid economic growth. As a result, a reduction in spending on Chinese products and services, the institution of additional tariffs or other trade barriers, including as a result of heightened trade tensions between China and the U.S., or a downturn in any of the economies of China’s key trading partners may have an adverse impact on the Chinese economy. Any difficulties of the Public Company Accounting Oversight Board (“PCAOB”) to inspect audit work papers and practices of PCAOB-registered accounting firms in China with respect to their audit work of U.S. reporting companies may impose significant additional risks associated with investments in China. Certain securities <div style="line-height: 12.10pt; margin-left: 14.97pt; margin-top: 0.00pt; text-align: left;">issued by companies located or operating in China, such as China A-shares, are subject to trading restrictions and suspensions, quota limitations and sudden changes in those limitations, and operational, clearing and settlement risks.</div><div style="margin-top: 6pt;">Additionally, the Fund may gain exposure to certain companies in China through legal structures known as variable interest entities ("VIEs"), which provide exposure to Chinese companies through contractual arrangements instead of equity ownership. The China Securities Regulatory Commission ("CSRC") released new rules that permit the use of VIE structures, provided they abide by Chinese laws and register with the CSRC. The rules, however, may cause Chinese companies to undergo greater scrutiny and may make the process to create VIEs more difficult and costly. Further, while the rules and implementing guidelines do not prohibit the use of VIE structures, this does not serve as a formal endorsement either. There is a risk that the Chinese government may cease to tolerate VIEs at any time, and any guidance or further rulemaking prohibiting or restricting these structures by the Chinese government, generally or with respect to specific industries, would likely cause impacted VIE-structured holding(s) to suffer significant, detrimental, and possibly permanent losses.</div>•India Investment Risk is the risk associated with investments in companies located or operating in India, such as political and legal uncertainty, greater government control over the economy, currency fluctuations or blockage, and the risk of nationalization or expropriation of assets, which may result in higher potential for losses. Specifically, India’s strained relations with neighboring countries like Pakistan and China could result in geopolitical risk that has an adverse impact on the Indian economy and stock market. In addition, the Reserve Bank of India (“RBI”) has imposed limits on foreign ownership of Indian securities, which may limit the amount the Fund can invest in certain types of companies. Further, certain Indian regulatory approvals, including approvals from the Securities and Exchange Board of India, the RBI, the central government and the tax authorities (to the extent that tax benefits need to be utilized), may be required before the Fund can make investments in the securities of Indian companies. Capital gains from Indian securities may be subject to local taxation.•Taiwan Investment Risk is the risk of investing in securities of Taiwanese issuers. Specifically, Taiwan’s geographic proximity and history of political contention with China have resulted in ongoing tensions between the two countries, which may materially affect the Taiwanese economy and its securities market. Investments in securities of Taiwanese companies are subject to Taiwan’s heavy dependence on exports. Reductions in spending on Taiwanese products and services, labor shortages, institution of tariffs or other trade barriers, or a downturn in any of the economies of Taiwan’s key trading partners, including the United States, may have an adverse impact on the Taiwanese economy and the values of Taiwanese companies. <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Depositary Receipts Risk Foreign securities may trade in the form of depositary receipts. In addition to investment risks associated with the underlying issuer, depositary receipts may expose the Fund to additional risks associated with non-uniform terms that apply to depositary receipt programs, including credit exposure to the depository bank and to the sponsors and other parties with whom the depository bank establishes the programs, currency, political, economic, market risks and the risks of an illiquid market for depositary receipts. Depositary receipts are generally subject to the same risks as the foreign securities that they evidence or into which they may be converted. Depositary receipts may not track the price of the underlying foreign securities on which they are based, may have limited voting rights, and may have a distribution subject to a fee charged by the depository. As a result, equity shares of the underlying issuer may trade at a discount or premium to the market price of the depositary receipts.</div> <div style="margin-top: 6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase. </div> <div style="margin-top: 6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;"> Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="margin-top: 6pt;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Value Investing Risk is the risk that the Fund’s investment in companies whose securities are believed to be undervalued, relative to their underlying profitability, will not appreciate in value as anticipated.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting. This risk may be heightened because of its investments in non-U.S. securities.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top: 6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div> •Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies.•Forward Foreign Currency Contracts Risk is the risk that, if forward prices increase, a loss will occur to the extent that the agreed upon purchase price of the currency exceeds the price of the currency that was agreed to be sold. <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> <div style="margin-top: 6pt;">Valuation Risk is the risk that the sale price the Fund could receive for a portfolio security may differ from the Fund’s valuation of the security, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. In addition, the value of the securities in the Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year and (B) how the Fund’s average annual returns compare with those of a broad measure of market performance. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year and (B) how the Fund’s average annual returns compare with those of a broad measure of market performance. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the periods in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (12/31/2020): 22.97% </div> <div style="margin-top: 6pt;">Worst Quarter (3/31/2020): -27.43%</div> Best Quarter 2020-12-31 0.2297 Worst Quarter 2020-03-31 -0.2743 Average Annual Total Returns (for the periods ended December 31, 2024) 0.0489 0.0281 0.0357 0.0412 0.0201 0.0287 0.0365 0.0216 0.0277 0.0750 0.0170 0.0364 0.0599 0.0381 0.0435 In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the Morningstar® Emerging Markets Factor Tilt IndexSM to the MSCI Emerging Markets Index. The Fund will continue to compare its performance to the Morningstar® Emerging Markets Factor Tilt IndexSM, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® US Quality Large Cap Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Northern Trust Quality Large Cap IndexSM (the “Underlying Index”).</div> Fees and Expenses of the Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0025 0.0000 0.0001 0.0026 -0.0001 0.0025 March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 26 83 145 330 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 16% of the average value of its portfolio. 0.16 Principal Investment Strategies <div style="margin-top: 6pt;">The Underlying Index is designed to reflect the performance of a selection of companies that, in aggregate, possess greater exposure to quality, value and momentum factors relative to a universe of publicly-traded U.S. large-capitalization equity securities. This universe (the “Eligible Universe”) is comprised of the 600 largest companies in the Northern Trust 1250 Index, a float-adjusted market-capitalization weighted index of U.S. companies, as determined by the Index Provider, at the time of reconstitution. The Underlying Index is designed to maximize exposure to the composite of factors (quality, value, and momentum) while minimizing the overall risk of the Underlying Index relative to the Eligible Universe. </div> <div style="margin-top: 6pt;">To derive the Underlying Index, NTI, acting in its capacity as index provider (the “Index Provider”), ranks all constituents of the Eligible Universe using a Northern Trust proprietary blended multi-factor score. This score is designed to measure companies based on the quantitative assessment of their respective (a) quality (i.e., a factor that seeks to identify companies that exhibit financial strength and stability relative to the Eligible Universe); (b) value </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">(i.e., a factor reflecting the current worth a company relative to its own historical value, book value or valuation versus peers); and (c) momentum (i.e., a factor that reflects market sentiment and changes in security price over a given time period). The Index Provider then uses an optimization process to select and weight eligible securities in order to maximize the overall blended multi-factor score relative to the Eligible Universe and to manage systematic risk utilizing several constraints. The optimization also includes sector, industry, single-security weight, beta (i.e. market sensitivity, relative to the Eligible Universe), liquidity, constituent and turnover constraints so that these index characteristics vary within acceptable bands relative to the Eligible Universe. The Underlying Index is reconstituted on a quarterly basis. The Fund generally reconstitutes its portfolio in accordance with the Underlying Index. As of December 31, 2024, the Underlying Index was comprised of 156 securities with a market capitalization ranging from $10.3 billion to $3.8 trillion. </div> <div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. </div> <div style="margin-top: 6pt;">NTI uses a representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div> <div style="margin-top: 6pt;">The Fund generally will invest under normal circumstances at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of its Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts and options on futures, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div> <div style="margin-top: 6pt;">The Underlying Index is created and sponsored by NTI, as the Index Provider. NTI also serves as the investment adviser to the Fund. The Index Provider determines the </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div> <div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received). </div> <div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the Information Technology sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the Information Technology sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time. Principal Risks <div style="margin-top: 6pt;">Equity Securities Risk is the risk that the values of the equity securities owned by the Fund may be more volatile and underperform other asset classes and the general securities markets.</div> <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> •Information Technology Sector Risk is the risk that securities of technology companies may be subject to greater price volatility than securities of companies in other sectors. These securities may fall in and out of favor with investors rapidly, which may cause sudden selling and dramatically lower market prices. Technology securities also may be affected adversely by changes in technology, consumer and business purchasing patterns, government regulation and/or obsolete products or services. <div style="margin-top: 6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase. </div> <div style="margin-top: 6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's abil</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">ity to adjust its exposure to required levels in order to track its Underlying Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="margin-top: 6pt;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Momentum Risk is the risk that securities that have had positive momentum compared to other securities may be more volatile than a broad cross-section of securities or that returns on securities that have previously exhibited positive momentum are less than returns on other securities or the overall stock market. Momentum can turn quickly and cause significant variation from other types of investments.</div> <div style="margin-top: 6pt;">Value Investing Risk is the risk that the Fund’s investment in companies whose securities are believed to be undervalued, relative to their underlying profitability, will not appreciate in value as anticipated.</div> <div style="margin-top: 6pt;">Quality Factor Risk is the risk that the past performance of companies that have exhibited quality characteristics does not continue or the returns on securities issued by such companies may be less than returns from other styles of investing or the overall stock market. There may be periods when quality investing is out of favor and during which time the Fund's performance may suffer.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Par</div><div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">ticipants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div><div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top: 6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div>•Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies. <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those </div><div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the periods in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (6/30/2020): 20.80% </div> <div style="margin-top: 6pt;">Worst Quarter (3/31/2020): -21.73%</div> Best Quarter 2020-06-30 0.2080 Worst Quarter 2020-03-31 -0.2173 Average Annual Total Returns (for the periods ended December 31, 2024) 0.2668 0.1404 0.1282 2015-09-23 0.2635 0.1368 0.1241 0.1600 0.1120 0.1055 0.2502 0.1452 0.1475 0.2702 0.1438 0.1316 Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return beforetaxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® STOXX® US ESG Select Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the STOXX® USA ESG Select KPIs IndexSM (the “Underlying Index”). </div> Fees and Expenses of the Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0032 0.0000 0.0001 0.0033 -0.0001 0.0032 March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The Example also assumes that your investment has a 5% </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 33 105 184 417 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 27% of the average value of its portfolio. 0.27 Principal Investment Strategies <div style="margin-top: 6pt;">The Underlying Index is designed to reflect the performance of a selection of companies that, in aggregate, score better with respect to a set of environmental, social and governance (“ESG”) key performance indicators (“KPIs”) relative to the U.S. companies in the STOXX® Global 1800 Index (the “Parent Index”), a float-adjusted market-capitalization weighted index of companies incorporated in the U.S. and in developed international markets. The Underlying Index seeks to display enhanced ESG and risk-return characteristics relative to the broad U.S. large-cap equity market by featuring ESG-related KPIs as determined by STOXX Ltd. (the “Index Provider”). </div> <div style="margin-top: 6pt;">To derive the Underlying Index, the Index Provider eliminates all non-U.S. companies from the Parent Index. From the Parent Index, the Index Provider also eliminates companies that are non-compliant based on Sustainalytics Global Standards Screening assessment or have certain levels of involvement with the following products, services, or industries: (i) controversial weapons, (ii) small arms, (iii) military contracting, (iv) unconventional oil & gas, (v) thermal coal, (vi) tobacco, and (vii) private prisons. The Index Provider also eliminates companies based on cus</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">tomer incidents controversy ratings. For each remaining company, the KPIs are determined and standardized by industry, and an aggregate ESG score is calculated. The companies with an ESG score lower than the median ESG score within each industry are then dropped from the Underlying Index. The weights of the remaining constituents are then adjusted so that higher scoring ESG companies are assigned greater weights compared to the Parent Index. The maximum weight that can be assigned to a single company is limited to 5% at the time of each index rebalancing or reconstitution. As of December 31, 2024, the Underlying Index consisted of 261 U.S. companies with market capitalizations ranging from $11.7 billion to $3.8 trillion. The Underlying Index is reviewed on a quarterly basis. The Fund generally reconstitutes or rebalances its portfolio in accordance with the Underlying Index. </div> <div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. </div> <div style="margin-top: 6pt;">NTI uses a representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div> <div style="margin-top: 6pt;">Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts and options on futures contracts, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div> <div style="margin-top: 6pt;">The Underlying Index is sponsored by the Index Provider, an organization that is independent of the Fund and NTI. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div> <div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received). </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the Information Technology sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time. </div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the Information Technology sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time. Principal Risks <div style="margin-top: 6pt;">ESG Investment Risk is the risk that because the Index Provider includes and excludes issuers and assigns weights to issuers in the Underlying Index by applying nonfinancial factors, the Fund may underperform the broader equity market or other funds that do or do not use ESG factors, scores, or screens in their securities selection process, or use a different ESG methodology. The ESG methodology of the Underlying Index will affect the Fund’s exposure to certain companies and sectors and may adversely affect the Fund’s performance depending on whether such companies and sectors are in or out of favor. Although the Underlying Index is designed to measure a portfolio of companies with certain ESG characteristics, there is no assurance that every security in the Underlying Index or Fund will have ESG characteristics or that companies that have historically exhibited such characteristics will continue to exhibit such characteristics. There is also the risk that the Fund may have indirect exposure to companies that have been excluded from the Underlying Index through its use of certain derivative instruments. </div> <div style="margin-top: 6pt;">Currently, there is a lack of common industry standards relating to the development and application of ESG criteria, which may make it difficult to compare the Fund’s </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">principal investment strategies with the investment strategies of other funds that integrate certain ESG criteria. The subjective value that investors may assign to certain types of ESG characteristics may differ substantially from that of the assessment by the Index Provider or a data provider. Investors can differ in their views of what constitutes positive or negative ESG characteristics. As a result, the Fund may invest in companies that do not reflect the beliefs and values of any particular investor. A company included in the Underlying Index may not exhibit positive or favorable ESG characteristics. The companies selected by the Index Provider as demonstrating certain ESG characteristics may not be the same companies selected by other index providers or investment managers as exhibiting those characteristics. </div> <div style="margin-top: 6pt;">The Index Provider relies on various sources of information regarding an issuer, including information that may be based on assumptions and estimates. ESG information from third-party data providers may be incomplete, inaccurate or unavailable. Neither the Fund nor NTI can offer assurances that the Underlying Index’s methodology or sources of information will provide an accurate assessment of the issuers of the securities included in the Fund’s Underlying Index. The Index Provider uses third-party data that it believes to be reliable, but it does not guarantee the accuracy of such third-party data. Data can vary across providers or within industries. ESG standards differ by region and industry, and a company’s ESG practices or the Index Provider’s or data providers’ assessment of a company’s ESG practices may change over time. Regulatory changes or interpretations regarding the definitions and/or use of ESG criteria could have a material adverse effect on the Fund’s ability to invest in accordance with its investment policies and/or achieve its investment objective.</div> <div style="margin-top: 6pt;">Equity Securities Risk is the risk that the values of the equity securities owned by the Fund may be more volatile and underperform other asset classes and the general securities markets.</div> <div style="margin-top: 6pt;">Mid Cap Stock Risk is the risk that stocks of mid-sized companies may be subject to more abrupt or erratic market movements than stocks of larger, more established companies, and may lack sufficient market liquidity. Mid-sized companies may have limited product lines or financial resources, and may be dependent upon a particular niche </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">of the market, or may be dependent upon a small or inexperienced management group. Securities of smaller companies may trade less frequently and in lower volume than the securities of larger companies, which could lead to higher transaction costs. Generally the smaller the company size, the greater the risk.</div> <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> •Information Technology Sector Risk is the risk that securities of technology companies may be subject to greater price volatility than securities of companies in other sectors. These securities may fall in and out of favor with investors rapidly, which may cause sudden selling and dramatically lower market prices. Technology securities also may be affected adversely by changes in technology, consumer and business purchasing patterns, government regulation and/or obsolete products or services. <div style="margin-top: 6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase. </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="margin-top: 6pt;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;"> transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top: 6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div> •Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies. <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the periods in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (6/30/2020): 21.11% </div> <div style="margin-top: 6pt;">Worst Quarter (3/31/2020): -19.00%</div> Best Quarter 2020-06-30 0.2111 Worst Quarter 2020-03-31 -0.1900 Average Annual Total Returns (for the periods ended December 31, 2024) 0.2028 0.1387 0.1438 2016-07-13 0.1993 0.1351 0.1398 0.1224 0.1106 0.1187 0.2013 0.1368 0.1397 0.2451 0.1427 0.1439 Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;"> plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® STOXX® Global ESG Select Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the STOXX® Global ESG Select KPIs IndexSM (the “Underlying Index”).</div> Fees and Expenses of the Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0042 0.0000 0.0002 0.0044 -0.0002 0.0042 March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 43 139 244 553 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 41% of the average value of its portfolio. 0.41 Principal Investment Strategies <div style="margin-top: 6pt;">The Underlying Index is designed to reflect the performance of a selection of companies that, in aggregate, score better with respect to a set of environmental, social and governance (“ESG”) key performance indicators (“KPIs”) relative to the STOXX® Global 1800 Index (the “Parent Index”), a float-adjusted market-capitalization weighted index of companies incorporated in the U.S. and in developed international markets. The Underlying Index seeks to display enhanced ESG and risk-return characteristics relative to the Parent Index by featuring ESG-related KPIs, as determined by STOXX Ltd. (the “Index Provider”). </div> <div style="margin-top: 6pt;">To derive the Underlying Index, the Index Provider eliminates companies that are non-compliant based on Sustainalytics Global Standards Screening assessment or have certain levels of involvement with the following products, services, or industries: (i) controversial weapons, (ii) small arms, (iii) military contracting, (iv) unconventional oil & gas, (v) thermal coal, (vi) tobacco, and (vii) private prisons. The Index Provider also eliminates companies based on customer incidents controversy ratings. For each remaining company, the KPIs are determined and standardized by industry, and an aggregate ESG score is calcu</div> <div style="line-height: 12.10pt; margin-top: 0.00pt; text-align: left;">lated. The companies with an ESG score lower than the median ESG score within each industry are then dropped from the Underlying Index. The weights of the remaining constituents are then adjusted so that higher scoring ESG companies are assigned greater weights compared to the Parent Index. Component weightings may also be adjusted to ensure that the weight representation of each country in the Underlying Index does not vary from that in the STOXX® Global 1800 Index by more than +/-1 percentage point and that the weight of a single company is limited to 5% at the time of each index rebalancing or reconstitution. As of December 31, 2024, the Underlying Index consisted of 862 companies with market capitalizations ranging from $445.5 million to $2.1 trillion. The Underlying Index is reviewed on a quarterly basis. The Fund generally reconstitutes or rebalances its portfolio in accordance with the Underlying Index. </div> <div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. </div> <div style="margin-top: 6pt;">NTI uses a representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div> <div style="margin-top: 6pt;">Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index and in American Depositary Receipts (“ADRs”) and Global Depositary Receipts (“GDRs”) (collectively “Depositary Receipts”) based on the securities in the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts, options on futures contracts and forward currency contracts, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. The Fund may enter into forward foreign currency exchange contracts in order to facilitate local settlements or to protect against currency exposure in connection with their distributions to shareholders. The Fund does not expect to engage in currency transactions for speculative purposes or for purposes of hedging against declines in the value of its assets that are denominated in a foreign currency. </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">The Underlying Index is sponsored by the Index Provider, an organization that is independent of the Fund and NTI. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div> <div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received). </div> <div style="margin-top: 6pt;">From time to time the Fund may focus its investments (i.e., invest more than 15% of its total assets) in one or more particular countries or geographic regions. </div> <div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the Information Technology sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time. </div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the Information Technology sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time. Principal Risks <div style="margin-top: 6pt;">ESG Investment Risk is the risk that because the Index Provider includes and excludes issuers and assigns weights to issuers in the Underlying Index by applying nonfinancial factors, the Fund may underperform the broader equity market or other funds that do or do not use ESG factors, scores, or screens in their securities selection process, or use a different ESG methodology. The ESG methodology of </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">the Underlying Index will affect the Fund’s exposure to certain companies and sectors and may adversely affect the Fund’s performance depending on whether such companies and sectors are in or out of favor. Although the Underlying Index is designed to measure a portfolio of companies with certain ESG characteristics, there is no assurance that every security in the Underlying Index or Fund will have ESG characteristics or that companies that have historically exhibited such characteristics will continue to exhibit such characteristics. There is also the risk that the Fund may have indirect exposure to companies that have been excluded from the Underlying Index through its use of certain derivative instruments. </div> <div style="margin-top: 6pt;">Currently, there is a lack of common industry standards relating to the development and application of ESG criteria, which may make it difficult to compare the Fund’s principal investment strategies with the investment strategies of other funds that integrate certain ESG criteria. The subjective value that investors may assign to certain types of ESG characteristics may differ substantially from that of the assessment by the Index Provider or a data provider. Investors can differ in their views of what constitutes positive or negative ESG characteristics. As a result, the Fund may invest in companies that do not reflect the beliefs and values of any particular investor. A company included in the Underlying Index may not exhibit positive or favorable ESG characteristics. The companies selected by the Index Provider as demonstrating certain ESG characteristics may not be the same companies selected by other index providers or investment managers as exhibiting those characteristics. </div> <div style="margin-top: 6pt;">The Index Provider relies on various sources of information regarding an issuer, including information that may be based on assumptions and estimates. ESG information from third-party data providers may be incomplete, inaccurate or unavailable. Neither the Fund nor NTI can offer assurances that the Underlying Index’s methodology or sources of information will provide an accurate assessment of the issuers of the securities included in the Fund’s Underlying Index. The Index Provider uses third-party data that it believes to be reliable, but it does not guarantee the accuracy of such third-party data. Data can vary across providers or within industries. ESG standards differ by region and industry, and a company’s ESG practices or the Index Provider’s or data providers’ assessment of a company’s</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;"> ESG practices may change over time. Regulatory changes or interpretations regarding the definitions and/or use of ESG criteria could have a material adverse effect on the Fund’s ability to invest in accordance with its investment policies and/or achieve its investment objective.</div> <div style="margin-top: 6pt;">Equity Securities Risk is the risk that the values of the equity securities owned by the Fund may be more volatile and underperform other asset classes and the general securities markets.</div> <div style="margin-top: 6pt;">Mid Cap Stock Risk is the risk that stocks of mid-sized companies may be subject to more abrupt or erratic market movements than stocks of larger, more established companies, and may lack sufficient market liquidity. Mid-sized companies may have limited product lines or financial resources, and may be dependent upon a particular niche of the market, or may be dependent upon a small or inexperienced management group. Securities of smaller companies may trade less frequently and in lower volume than the securities of larger companies, which could lead to higher transaction costs. Generally the smaller the company size, the greater the risk.</div> <div style="margin-top: 6pt;">Depositary Receipts Risk Foreign securities may trade in the form of depositary receipts. In addition to investment risks associated with the underlying issuer, depositary receipts may expose the Fund to additional risks associated with non-uniform terms that apply to depositary receipt programs, including credit exposure to the depository bank and to the sponsors and other parties with whom the depository bank establishes the programs, currency, political, economic, market risks and the risks of an illiquid market for depositary receipts. Depositary receipts are generally subject to the same risks as the foreign securities that they evidence or into which they may be converted. Depositary receipts may not track the price of the underlying foreign securities on which they are based, may have limited voting rights, and may have a distribution subject to a fee charged by the depository. As a result, equity shares of the underlying issuer may trade at a discount or premium to the market price of the depositary receipts.</div> <div style="margin-top: 6pt;">Foreign Securities Risk is the risk that investing in foreign (non-U.S.) securities may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies, due to less liquid markets and adverse economic, political, diplomatic,</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;"> financial, and regulatory factors. Foreign governments may impose limitations on foreigners’ ownership of interests in local issuers, restrictions on the ability to repatriate assets, and may also impose taxes. Any of these events could cause the value of the Fund’s investments to decline. Foreign banks, agents and securities depositories that hold the Fund’s foreign assets may be subject to little or no regulatory oversight over, or independent evaluation, of their operations. Additional costs associated with investments in foreign securities may include higher custodial fees than those applicable to domestic custodial arrangements and transaction costs of foreign currency conversions. Unless the Fund has hedged its foreign currency exposure, foreign securities risk also involves the risk of negative foreign currency rate fluctuations, which may cause the value of securities denominated in such foreign currency (or other instruments through which the Fund has exposure to foreign currencies) to decline in value. Currency exchange rates may fluctuate significantly over short periods of time. Currency hedging strategies, if used, are not always successful. For instance, forward foreign currency exchange contracts, if used by the Fund, could reduce performance if there are unanticipated changes in currency exchange rates.</div> <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> •Information Technology Sector Risk is the risk that securities of technology companies may be subject to greater price volatility than securities of companies in other sectors. These securities may fall in and out of favor with investors rapidly, which may cause sudden selling and dramatically lower market prices. Technology securities also may be affected adversely by changes in technology, consumer and business purchasing patterns, government regulation and/or obsolete products or services. <div style="margin-top: 6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase. </div> <div style="margin-top: 6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="margin-top: 6pt;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting. This risk may be heightened because of its investments in non-U.S. securities.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top: 6pt;">Geographic Risk is the risk that if the Fund invests a significant portion of its total assets in certain issuers within the same country or geographic region, an adverse economic, business or political development affecting that country or region may affect the value of the Fund’s investments more, and the Fund’s investments may be more volatile, than if the Fund’s investments were not so concentrated in such country or region.</div> <div style="margin-top: 6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div> •Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies.•Forward Foreign Currency Contracts Risk is the risk that, if forward prices increase, a loss will occur to the extent that the agreed upon purchase price of the currency exceeds the price of the currency that was agreed to be sold. <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> <div style="margin-top: 6pt;">Valuation Risk is the risk that the sale price the Fund could receive for a portfolio security may differ from the Fund’s valuation of the security, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. In addition, the value of the securities in the Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the periods in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (6/30/2020): 18.93% </div> <div style="margin-top: 6pt;">Worst Quarter (3/31/2020): -19.31%</div> Best Quarter 2020-06-30 0.1893 Worst Quarter 2020-03-31 -0.1931 Average Annual Total Returns (for the periods ended December 31, 2024) 0.1481 0.1129 0.1206 2016-07-13 0.1431 0.1084 0.1157 0.0911 0.0892 0.0981 0.1490 0.1137 0.1210 0.1867 0.1116 0.1155 Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® ESG & Climate US Large Cap Core Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Northern Trust ESG & Climate US Large Cap Core IndexSM (the “Underlying Index”).</div> Fees and Expenses of the Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0009 0.0000 0.0001 0.0010 -0.0001 0.0009 March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 9 31 55 127 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 32% of the average value of its portfolio. 0.32 Principal Investment Strategies <div style="margin-top: 6pt;">The Underlying Index, administered by NTI in its capacity as index provider (the “Index Provider”), is designed to reflect the performance of a selection of companies that exhibit certain environmental, social and governance (“ESG”) characteristics in the aggregate, while also seeking to provide broad-market, core exposure to publicly-traded U.S. large capitalization equity securities, i.e., the constituents in the Northern Trust 600 IndexSM (the “Eligible Universe”), as measured by their float adjusted market capitalization. The Northern Trust 600 IndexSM is a float-adjusted market-capitalization weighted index of US domiciled companies. </div> <div style="margin-top: 6pt;">The Underlying Index starts by excluding certain companies from the Eligible Universe that, based on third-party data, are determined to have certain levels of controversial business involvement or behavior, including in tobacco, weaponry, thermal coal, unconventional oil and gas, and for-profit prisons, or to have caused, contributed to or are linked to certain violations of international norms and standards. Such exclusions are based on percentage of revenue thresholds for certain categories (e.g., those that </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">receive significant revenue from production, retail and distribution of civilian weapons) and categorical exclusions for others (e.g., tobacco producers). The above-described exclusionary screens are applied with each reconstitution of the Underlying Index. The Index Provider may modify this list of excluded companies at any time, at its own discretion. </div> <div style="margin-top: 6pt;">The Underlying Index next applies an optimization process to minimize variance to the Eligible Universe while also targeting certain ESG characteristics, which is designed to produce an index that, relative to the Eligible Universe: (a) has an aggregate higher scoring of certain ESG characteristics, as measured by the Northern Trust ESG Vector Score (“ESG Vector Score”) described below, (b) improves the carbon risk rating, as measured by certain carbon-related risk metrics, and (c) decreases the weighted average carbon intensity and potential emissions. </div> <div style="margin-top: 6pt;">The ESG Vector Score is designed to rank companies based on their management of and exposure to material ESG metrics as defined by the Sustainability Accounting Standards Board (“SASB”) Standards. In addition, the Index Provider uses available data from Institutional Shareholder Services ESG Solutions to assess carbon emissions intensity, carbon reserves and a carbon risk rating. Carbon emissions intensity measures (i) direct greenhouse gas emissions from sources controlled or owned by the company (e.g., emissions associated with fuel combustion in boilers, furnaces, or vehicles); and (ii) indirect greenhouse gas emissions associated with the purchase of electricity, steam, heat or cooling against sales by the company. Carbon reserves measure the total estimated greenhouse gas emissions attributable to a company’s fossil fuel reserve assets. The carbon risk rating provides an assessment of a company’s ability to mitigate the risks of transition to a lower carbon economy based on its specific baseline carbon risk exposure. </div> <div style="margin-top: 6pt;">In the event that metrics or other data used to construct the ESG Vector Score as well as carbon emissions intensity, carbon reserves and/or the carbon risk rating are not available or otherwise deemed unreliable, NTI may make reasonable estimates or otherwise exercise its discretion to implement the optimization process. </div> <div style="margin-top: 6pt;">Notwithstanding the optimization process, it is possible that the Underlying Index will include (and therefore the Fund could invest in) securities that, individually, have a </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">lower ESG Vector Score, lower carbon risk rating, or higher emissions relative to the weighted average of the Eligible Universe. The optimization process also includes constituent, liquidity, turnover, sector, industry group and weight constraints so that these characteristics in the Underlying Index vary within acceptable bands relative to the Eligible Universe.</div> <div style="margin-top: 6pt;">As of December 31, 2024, the Underlying Index was comprised of 133 constituents with market capitalizations ranging from $9.9 billion to $3.8 trillion. The Underlying Index will be reconstituted quarterly under normal market conditions. The Fund generally reconstitutes its portfolio in accordance with the Underlying Index. </div> <div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. </div> <div style="margin-top: 6pt;">NTI uses a representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div> <div style="margin-top: 6pt;">Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts and options on futures contracts, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div> <div style="margin-top: 6pt;">The Underlying Index is created and sponsored by NTI, as the Index Provider. NTI also serves as the investment adviser to the Fund. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div> <div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received). </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">The Fund is “non-diversified” under the Investment Company Act of 1940 (“1940 Act”), as amended, and may invest more of its assets in fewer issuers than “diversified” funds. </div> <div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the Information Technology sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time. </div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the Information Technology sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time. Principal Risks <div style="margin-top: 6pt;">ESG Investment Risk is the risk that because the Index Provider includes and excludes issuers and assigns weights to issuers in the Underlying Index by applying non-financial factors, the Fund may underperform the broader equity market or other funds that do or do not use ESG factors, scores, or screens in their securities selection process, or use a different ESG methodology. The ESG methodology of the Underlying Index will affect the Fund’s exposure to certain companies and sectors and may adversely affect the Fund’s performance depending on whether such companies and sectors are in or out of favor. Although the Underlying Index is designed to measure a portfolio of companies with certain ESG characteristics, there is no assurance that every security in the Underlying Index or Fund will have ESG characteristics or that companies that have historically exhibited such characteristics will continue to exhibit such characteristics. There is also the risk that the Fund may have indirect exposure to companies that have been excluded from the Underlying Index through its use of certain derivative instruments. </div> <div style="margin-top: 6pt;">Currently, there is a lack of common industry standards relating to the development and application of ESG criteria, which may make it difficult to compare the Fund’s principal investment strategies with the investment strategies of other funds that integrate certain ESG criteria. The subjective value that investors may assign to certain types of ESG characteristics may differ substantially from that of the assessment by the Index Provider or a data provider. Investors can differ in their views of what constitutes positive or negative ESG characteristics. As a result, the Fund may invest in companies that do not reflect the beliefs and values of any particular investor. A company included in the Underlying Index may not exhibit positive or favorable </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">ESG characteristics. The companies selected by the Index Provider as demonstrating certain ESG characteristics may not be the same companies selected by other index providers or investment managers as exhibiting those characteristics. </div> <div style="margin-top: 6pt;">The Index Provider relies on various sources of information regarding an issuer, including information that may be based on assumptions and estimates. ESG information from third-party data providers may be incomplete, inaccurate or unavailable. Neither the Fund nor NTI can offer assurances that the Underlying Index’s methodology or sources of information will provide an accurate assessment of the issuers of the securities included in the Fund’s Underlying Index. The Index Provider uses third-party data that it believes to be reliable, but it does not guarantee the accuracy of such third-party data. Data can vary across providers or within industries. ESG standards differ by region and industry, and a company’s ESG practices or the Index Provider’s or data providers’ assessment of a company’s ESG practices may change over time. Regulatory changes or interpretations regarding the definitions and/or use of ESG criteria could have a material adverse effect on the Fund’s ability to invest in accordance with its investment policies and/or achieve its investment objective.</div> <div style="margin-top: 6pt;">Equity Securities Risk is the risk that the values of the equity securities owned by the Fund may be more volatile and underperform other asset classes and the general securities markets.</div> <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> •Information Technology Sector Risk is the risk that securities of technology companies may be subject to greater price volatility than securities of companies in other sectors. These securities may fall in and out of favor with investors rapidly, which may cause sudden selling and dramatically lower market prices. Technology securities also may be affected adversely by changes in technology, consumer and business purchasing patterns, government regulation and/or obsolete products or services. <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase.</div> <div style="margin-top: 6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Underlying Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top: 6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div> •Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies. <div style="margin-top: 6pt;">New Fund Risk is the risk that the Fund will not grow to or maintain an economically viable size, in which case it may experience greater tracking error to its Underlying Index </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">than it otherwise would at higher asset levels, or it could ultimately liquidate without shareholder approval. The timing of such liquidation may not be favorable and could have negative tax consequences for shareholders. From time to time, an Authorized Participant, a third-party investor, the Fund’s adviser or an affiliate of the Fund’s adviser, may invest in the Fund and hold its investment for a specific period of time in order to facilitate commencement of the Fund’s operations or for the Fund to achieve size or scale. There can be no assurance that any such entity would not redeem its investment or that the size of the Fund would be maintained at such levels, which could negatively impact the Fund. The Fund’s Distributor does not maintain a secondary market in the shares.</div> <div style="margin-top: 6pt;">Non-Diversification Risk is the risk that because the Fund is non-diversified and may invest a larger percentage of its assets in the securities of fewer issuers than a diversified fund, the Fund’s performance will be more vulnerable to changes in the market value of a single issuer or group of issuers, and more susceptible to risks associated with a single economic, political or regulatory occurrence.</div> <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;"> indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com. </div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the period shown in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (12/31/2023): 11.66% </div> <div style="margin-top: 6pt;">Worst Quarter (6/30/2022): -16.14%</div> Best Quarter 2023-12-31 0.1166 Worst Quarter 2022-06-30 -0.1614 Average Annual Total Returns (for the periods ended December 31, 2024) 0.2312 0.1021 2021-09-20 0.2276 0.0985 0.1390 0.0791 0.2451 0.1038 0.2502 0.1127 0.2330 0.1029 In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the S&P 500 Index to the Russell 1000® Index. The Fund will continue to compare its performance to the S&P 500 Index, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® ESG & Climate Developed Markets ex-US Core Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Northern Trust ESG & Climate Developed Markets ex-US Core IndexSM (the “Underlying Index”).</div> Fees and Expenses of the Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0012 0.0000 0.0002 0.0014 -0.0002 0.0012 March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 12 43 77 177 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 22% of the average value of its portfolio. 0.22 Principal Investment Strategies <div style="margin-top: 6pt;">The Underlying Index, administered by NTI in its capacity as index provider (the “Index Provider”), is designed to reflect the performance of a selection of companies that exhibit certain environmental, social and governance (“ESG”) characteristics in the aggregate, while also seeking to provide broad-market, core exposure to publicly traded equity securities issued by companies domiciled in developed market countries, excluding the U.S., i.e., the constituents in the Northern Trust Developed Markets ex-US Large Cap IndexSM (the “Eligible Universe”).The Northern Trust Developed Markets ex-US Large Cap IndexSM is a sub-index of the Northern Trust Global IndexSM, where eligible securities are limited to those of companies that are domiciled in non-U.S. developed market countries and designated as large- or mid-capitalization companies by NTI. As of December 31, 2024, the Index Provider classifies the following as developed market countries outside of the U.S.: Australia, Austria, Belgium, Canada, Denmark, Finland, France, Germany, Hong Kong, Ireland, Israel, Italy, Japan, Netherlands, New Zealand, Norway, Portugal, Singapore, Spain, Sweden, Switzerland and United Kingdom. </div><div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">The Underlying Index starts by excluding certain companies from the Eligible Universe that, based on third-party data, are determined to have certain levels of controversial business involvement or behavior, including in tobacco, weaponry, thermal coal, unconventional oil and gas, and for-profit prisons, or to have caused, contributed to or are linked to certain violations of international norms and standards. Such exclusions are based on percentage of revenue thresholds for certain categories (e.g., those that receive significant revenue from production, retail and distribution of civilian weapons) and categorical exclusions for others (e.g., tobacco producers). The above-described exclusionary screens are applied with each reconstitution of the Underlying Index. The Index Provider may modify this list of excluded companies at any time, at its own discretion. </div><div style="margin-top: 6pt;">The Underlying Index next applies an optimization process to minimize variance to the Eligible Universe while also targeting certain ESG characteristics, which is designed to produce an index that, relative to the Eligible Universe: (a) has an aggregate higher scoring of certain ESG characteristics, as measured by the Northern Trust ESG Vector Score (“ESG Vector Score”) described below, (b) improves the carbon risk rating, as measured by certain carbon-related risk metrics, and (c) decreases the weighted average carbon intensity and potential emissions. </div><div style="margin-top: 6pt;">The ESG Vector Score is designed to rank companies based on their management of and exposure to material ESG metrics as defined by the Sustainability Accounting Standards Board (“SASB”) Standards. In addition, the Index Provider uses available data from Institutional Shareholder Services ESG Solutions to assess carbon emissions intensity, carbon reserves and a carbon risk rating. Carbon emissions intensity measures (i) direct greenhouse gas emissions from sources controlled or owned by the company (e.g., emissions associated with fuel combustion in boilers, furnaces, or vehicles); and (ii) indirect greenhouse gas emissions associated with the purchase of electricity, steam, heat or cooling against sales by the company. Carbon reserves measure the total estimated greenhouse gas emissions attributable to a company’s fossil fuel reserve assets. The carbon risk rating provides an assessment of a company’s ability to mitigate the risks of transition to a lower carbon economy based on its specific baseline carbon risk exposure. </div><div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">In the event that metrics or other data used to construct the ESG Vector Score as well as carbon emissions intensity, carbon reserves and/or the carbon risk rating are not available or otherwise deemed unreliable, NTI may make reasonable estimates or otherwise exercise its discretion to implement the optimization process. </div><div style="margin-top: 6pt;">Notwithstanding the optimization process, it is possible that the Underlying Index will include (and therefore the Fund could invest in) securities that, individually, have a lower ESG Vector Score, lower carbon risk rating, or higher emissions relative to the weighted average of the Eligible Universe. The optimization process also includes constituent, liquidity, turnover, country, region, sector, industry group and weight constraints so that these characteristics in the Underlying Index vary within acceptable bands relative to the Eligible Universe.</div><div style="margin-top: 6pt;">As of December 31, 2024, the Underlying Index was comprised of 240 constituents with market capitalizations ranging from $5.3 billion to $483.8 billion. The Underlying Index is reconstituted quarterly under normal market conditions. The Fund generally reconstitutes its portfolio in accordance with the Underlying Index. </div><div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. </div><div style="margin-top: 6pt;">NTI uses a representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div><div style="margin-top: 6pt;">Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index and in American Depositary Receipts (“ADRs”) and Global Depositary Receipts (“GDRs”) (collectively “Depositary Receipts”) based on the securities in the Underlying Index. The Fund may also invest up to 20% of its assets in cash </div><div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts, options on futures contracts and forward currency contracts, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. The Fund usually, but not always, pursues a strategy of being fully invested by exposing all or a portion of its cash to the performance of certain markets by purchasing index futures contracts (also known as “equitization”). This is intended to cause the Fund to perform as though its cash were actually invested in those markets. This futures exposure may or may not match the Fund’s Underlying Index and create indirect exposure to companies that have been excluded from the Underlying Index. The Fund will not invest directly in securities that have been excluded from the Fund’s Underlying Index. </div><div style="margin-top: 6pt;">The Underlying Index is created and sponsored by NTI, as the Index Provider. NTI also serves as the investment adviser to the Fund. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div><div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received). </div><div style="margin-top: 6pt;">From time to time the Fund may focus its investments (i.e., invest more than 15% of its total) in one or more particular countries or geographic regions. As of December 31, 2024, the Fund focused its investments in Japan.</div><div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. Principal Risks <div style="margin-top: 6pt;">ESG Investment Risk is the risk that because the Index Provider includes and excludes issuers and assigns weights to issuers in the Underlying Index by applying non-financial factors, the Fund may underperform the broader equity market or other funds that do or do not use ESG factors, scores, or screens in their securities selection process, or use a different ESG methodology. The ESG methodology of the Underlying Index will affect the Fund’s </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">exposure to certain companies and sectors and may adversely affect the Fund’s performance depending on whether such companies and sectors are in or out of favor. Although the Underlying Index is designed to measure a portfolio of companies with certain ESG characteristics, there is no assurance that every security in the Underlying Index or Fund will have ESG characteristics or that companies that have historically exhibited such characteristics will continue to exhibit such characteristics. There is also the risk that the Fund may have indirect exposure to companies that have been excluded from the Underlying Index through its use of certain derivative instruments. </div> <div style="margin-top: 6pt;">Currently, there is a lack of common industry standards relating to the development and application of ESG criteria, which may make it difficult to compare the Fund’s principal investment strategies with the investment strategies of other funds that integrate certain ESG criteria. The subjective value that investors may assign to certain types of ESG characteristics may differ substantially from that of the assessment by the Index Provider or a data provider. Investors can differ in their views of what constitutes positive or negative ESG characteristics. As a result, the Fund may invest in companies that do not reflect the beliefs and values of any particular investor. A company included in the Underlying Index may not exhibit positive or favorable ESG characteristics. The companies selected by the Index Provider as demonstrating certain ESG characteristics may not be the same companies selected by other index providers or investment managers as exhibiting those characteristics. </div> <div style="margin-top: 6pt;">The Index Provider relies on various sources of information regarding an issuer, including information that may be based on assumptions and estimates. ESG information from third-party data providers may be incomplete, inaccurate or unavailable. Neither the Fund nor NTI can offer assurances that the Underlying Index’s methodology or sources of information will provide an accurate assessment of the issuers of the securities included in the Fund’s Underlying Index. The Index Provider uses third-party data that it believes to be reliable, but it does not guarantee the accuracy of such third-party data. Data can vary across providers or within industries. ESG standards differ by region and industry, and a company’s ESG practices or the Index Provider’s or data providers’ assessment of a company’s ESG practices may change over time. Regulatory </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">changes or interpretations regarding the definitions and/or use of ESG criteria could have a material adverse effect on the Fund’s ability to invest in accordance with its investment policies and/or achieve its investment objective.</div> <div style="margin-top: 6pt;">Foreign Securities Risk is the risk that investing in foreign (non-U.S.) securities may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies, due to less liquid markets and adverse economic, political, diplomatic, financial, and regulatory factors. Foreign governments may impose limitations on foreigners’ ownership of interests in local issuers, restrictions on the ability to repatriate assets, and may also impose taxes. Any of these events could cause the value of the Fund’s investments to decline. Foreign banks, agents and securities depositories that hold the Fund’s foreign assets may be subject to little or no regulatory oversight over, or independent evaluation, of their operations. Additional costs associated with investments in foreign securities may include higher custodial fees than those applicable to domestic custodial arrangements and transaction costs of foreign currency conversions. Unless the Fund has hedged its foreign currency exposure, foreign securities risk also involves the risk of negative foreign currency rate fluctuations, which may cause the value of securities denominated in such foreign currency (or other instruments through which the Fund has exposure to foreign currencies) to decline in value. Currency exchange rates may fluctuate significantly over short periods of time. Currency hedging strategies, if used, are not always successful. For instance, forward foreign currency exchange contracts, if used by the Fund, could reduce performance if there are unanticipated changes in currency exchange rates.</div> <div style="margin-top: 6pt;">Geographic Risk is the risk that if the Fund invests a significant portion of its total assets in certain issuers within the same country or geographic region, an adverse economic, business or political development affecting that country or region may affect the value of the Fund’s investments more, and the Fund’s investments may be more volatile, than if the Fund’s investments were not so concentrated in such country or region.</div>•Japan Investment Risk is the risk of investing in securities of Japanese issuers. The Japanese economy may be subject to considerable degrees of economic, political and social instability, which could negatively impact Japanese issuers. In recent times, Japan’s economic growth rate has remained low, and it may remain low in the future. In addition, Japan is subject to the risk of natural disasters, such as earthquakes, volcanic eruptions, typhoons and tsunamis, which could negatively affect the securities of Japanese companies held by the Fund. <div style="margin-top: 6pt;">Depositary Receipts Risk Foreign securities may trade in the form of depositary receipts. In addition to investment risks associated with the underlying issuer, depositary receipts may expose the Fund to additional risks associated with non-uniform terms that apply to depositary receipt programs, including credit exposure to the depository bank and to the sponsors and other parties with whom the depository bank establishes the programs, currency, political, economic, market risks and the risks of an illiquid market for depositary receipts. Depositary receipts are generally subject to the same risks as the foreign securities that they evidence or into which they may be converted. Depositary receipts may not track the price of the underlying foreign securities on which they are based, may have limited voting rights, and may have a distribution subject to a fee charged by the depository. As a result, equity shares of the underlying issuer may trade at a discount or premium to the market price of the depositary receipts.</div> <div style="margin-top: 6pt;">Equity Securities Risk is the risk that the values of the equity securities owned by the Fund may be more volatile and underperform other asset classes and the general securities markets.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Mid Cap Stock Risk is the risk that stocks of mid-sized companies may be subject to more abrupt or erratic market movements than stocks of larger, more established companies, and may lack sufficient market liquidity. Mid-sized companies may have limited product lines or financial resources, and may be dependent upon a particular niche of the market, or may be dependent upon a small or inexperienced management group. Securities of smaller companies may trade less frequently and in lower volume than the securities of larger companies, which could lead to higher transaction costs. Generally the smaller the company size, the greater the risk.</div> <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> <div style="margin-top: 6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase.</div> <div style="margin-top: 6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Underlying Index or cause delays in the Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="margin-top: 6pt;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting. This risk may be heightened because of its investments in non-U.S. securities.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund’s holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top: 6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div> •Forward Foreign Currency Contracts Risk is the risk that, if forward prices increase, a loss will occur to the extent that the agreed upon purchase price of the currency exceeds the price of the currency that was agreed to be sold.•Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies. <div style="margin-top: 6pt;">New Fund Risk is the risk that the Fund will not grow to or maintain an economically viable size, in which case it may experience greater tracking error to its Underlying Index than it otherwise would at higher asset levels, or it could ultimately liquidate without shareholder approval. The timing of such liquidation may not be favorable and could have negative tax consequences for shareholders. From time to time, an Authorized Participant, a third-party investor, the Fund’s adviser or an affiliate of the Fund’s adviser, may invest in the Fund and hold its investment for a specific period of time in order to facilitate commencement of the Fund’s operations or for the Fund to achieve size or scale. There can be no assurance that any such entity would not redeem its investment or that the size of the Fund would be maintained at such levels, which could negatively impact the Fund. The Fund’s Distributor does not maintain a secondary market in the shares.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> <div style="margin-top: 6pt;">Valuation Risk is the risk that the sale price the Fund could receive for a portfolio security may differ from the Fund’s valuation of the security, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. In addition, the value of the securities in the Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com. </div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the period shown in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (12/31/2022): 15.92% </div> <div style="margin-top: 6pt;">Worst Quarter (6/30/2022): -14.17%</div> Best Quarter 2022-12-31 0.1592 Worst Quarter 2022-06-30 -0.1417 Average Annual Total Returns (for the periods ended December 31, 2024) 0.0319 0.0156 2021-09-20 0.0261 0.0108 0.0251 0.0132 0.0470 0.0234 0.0317 0.0155 Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® Morningstar Global Upstream Natural Resources Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Morningstar® Global Upstream Natural Resources IndexSM (the “Underlying Index”).</div> Fees And Expenses Of The Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0046 0.0000 0.0001 0.0047 -0.0001 0.0046 March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 47 150 262 590 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 21% of the average value of its portfolio. 0.21 Principal Investment Strategies <div style="margin-top: 6pt;">The Underlying Index is designed to reflect the performance of a selection of equity securities that are traded in or are issued by companies classified as developed or emerging markets (including the U.S.), as determined by Morningstar, Inc. (the “Index Provider”) pursuant to its index methodology. To be eligible for inclusion in the Underlying Index, a security must be issued by a company that has significant economic interests in one of the following natural resource categories: energy, agriculture, precious or industrial metals, timber or water, as determined by the Index Provider pursuant to its index methodology (collectively, the “Natural Resources sector”). Securities determined to be within the Natural Resources sector are then excluded from the Underlying Index if (i) they have an average daily traded value (three-month) of less than $1 million or (ii) for securities within the energy, agriculture or precious or industrial metals categories of the Natural Resources sector, they have a float market capitalization of less than $1 billion, or for securities within the timber or water categories of the Natural Resources sector, they have a float market capitalization of less than $500 million. The </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">largest stocks within each category are targeted for inclusion. Securities within the Underlying Index are then weighted based on their float adjusted market capitalization within each category of the Natural Resources sector, and weight caps are applied to limit exposure to any particular category within the Natural Resources sector, any individual security, the U.S. and emerging markets. </div> <div style="margin-top: 6pt;">As of December 31, 2024, the Underlying Index was comprised of 120 issues with market capitalizations ranging from $779.6 million to $1.8 trillion. The Underlying Index is reconstituted on a semi-annual basis and is rebalanced quarterly. The Fund generally rebalances and reconstitutes its portfolio in accordance with the Underlying Index. </div> <div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. </div> <div style="margin-top: 6pt;">NTI uses a representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div> <div style="margin-top: 6pt;">Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index and in American Depositary Receipts (“ADRs”) and Global Depositary Receipts (“GDRs”) (collectively “Depositary Receipts”) based on the securities in the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts, options on futures contracts and forward currency contracts, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div> <div style="margin-top: 6pt;">The Underlying Index is sponsored by the Index Provider, an organization that is independent of the Fund and NTI. The Index Provider determines the composition and rela</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">tive weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div> <div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received). </div> <div style="margin-top: 6pt;">From time to time the Fund may focus its investments (i.e., invest more than 15% of its total assets) in one or more particular countries or geographic regions. As of December 31, 2024, the Fund focused its investments in Canada.</div> <div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the Natural Resources sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the Natural Resources sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time. Principal Risks <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> •Natural Resources Sector Risk is the risk that the Fund is subject to the risks associated with investment in companies within the Natural Resources sector in addition to the general risk of the stock market. Companies <div style="line-height: 12.10pt; margin-left: 14.97pt; margin-top: 0.00pt; text-align: left;">within the Natural Resources sector can be significantly affected by events relating to U.S. and foreign political and economic developments and environmental and other government regulations, as well as other factors including, but not limited to: commodity price volatility, technological developments and natural or man-made disasters. Declines in the demand for, or prices of, natural resources generally would be expected to contribute to declines in the value of the Fund’s equity securities. Such declines may occur quickly and without warning and may negatively impact the value of the Fund and your investment.</div> <div style="margin-top: 6pt;">Equity Securities Risk is the risk that the values of the equity securities owned by the Fund may be more volatile and underperform other asset classes and the general securities markets.</div> <div style="margin-top: 6pt;">Foreign Securities Risk is the risk that investing in foreign (non-U.S.) securities may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies, due to less liquid markets and adverse economic, political, diplomatic, financial, and regulatory factors. Foreign governments may impose limitations on foreigners’ ownership of interests in local issuers, restrictions on the ability to repatriate assets, and may also impose taxes. Any of these events could cause the value of the Fund’s investments to decline. Foreign banks, agents and securities depositories that hold the Fund’s foreign assets may be subject to little or no regulatory oversight over, or independent evaluation, of their operations. Additional costs associated with investments in foreign securities may include higher custodial fees than those applicable to domestic custodial arrangements and transaction costs of foreign currency conversions. Unless the Fund has hedged its foreign currency exposure, foreign securities risk also involves the risk of negative foreign currency rate fluctuations, which may cause the value of securities denominated in such foreign currency (or other instruments through which the Fund has exposure to foreign currencies) to decline in value. Currency exchange rates may fluctuate significantly over short periods of time. Currency hedging strategies, if used, are not always successful. For instance, forward foreign currency exchange contracts, if used by the Fund, could reduce performance if there are unanticipated changes in currency exchange rates.</div> <div style="margin-top: 6pt;">Depositary Receipts Risk Foreign securities may trade in the form of depositary receipts. In addition to investment risks associated with the underlying issuer, depositary </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">receipts may expose the Fund to additional risks associated with non-uniform terms that apply to depositary receipt programs, including credit exposure to the depository bank and to the sponsors and other parties with whom the depository bank establishes the programs, currency, political, economic, market risks and the risks of an illiquid market for depositary receipts. Depositary receipts are generally subject to the same risks as the foreign securities that they evidence or into which they may be converted. Depositary receipts may not track the price of the underlying foreign securities on which they are based, may have limited voting rights, and may have a distribution subject to a fee charged by the depository. As a result, equity shares of the underlying issuer may trade at a discount or premium to the market price of the depositary receipts.</div> <div style="margin-top: 6pt;">Emerging Markets Risk is the risk that emerging markets are generally subject to greater market volatility, political, social and economic instability, uncertain trading markets and more governmental limitations on foreign investments than more developed markets. In addition, companies operating in emerging markets may be subject to lower trading volumes and greater price volatility than companies in more developed markets. Emerging market economies may be based on only a few industries, may be highly vulnerable to changes in local and global trade conditions, and may suffer from extreme and volatile debt burdens or inflation rates. Companies in emerging market countries generally may be subject to less stringent regulatory, disclosure, financial reporting, accounting, auditing and recordkeeping standards than companies in more developed countries. As a result, information, including financial information, about such companies may be less available and reliable, which can impede the Fund’s ability to evaluate such companies. Securities law and the enforcement of systems of taxation in many emerging market countries may change quickly and unpredictably, and the ability to bring and enforce actions (including bankruptcy, confiscatory taxation, expropriation, nationalization of a company’s assets, restrictions on foreign ownership of local companies, restrictions on withdrawing assets from the country, protectionist measures and practices such as share blocking), or to obtain information needed to pursue or enforce such actions, may be limited. Investments in emerging market securities may be subject to additional transaction costs, delays in settlement procedures, unexpected market closures, and lack of timely information.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Geographic Risk is the risk that if the Fund invests a significant portion of its total assets in certain issuers within the same country or geographic region, an adverse economic, business or political development affecting that country or region may affect the value of the Fund’s investments more, and the Fund’s investments may be more volatile, than if the Fund’s investments were not so concentrated in such country or region.</div>•Canada Investment Risk is the risk that theFund is particularly sensitive to political, economicand social conditions in affecting Canada. The Canadian economy is especially dependent on the demand for, and supply of, natural resources, and the Canadian market is relatively concentrated in issuers involved in the production and distribution of natural resources, particularly the production of metals. Any adverse events that affect Canada’s major industries may have a negative impact on the overall Canadian economy and the Fund. <div style="margin-top: 6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase. </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="margin-top: 6pt;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">NAV and possibly face trading halts and/or delisting. This risk may be heightened because of its investments in non-U.S. securities.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top: 6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div> •Forward Foreign Currency Contracts Risk is the risk that, if forward prices increase, a loss will occur to the extent that the agreed upon purchase price of the currency exceeds the price of the currency that was agreed to be sold.•Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies. <div style="margin-top: 6pt;">Mid and Small Cap Stock Risk is the risk that stocks of mid-sized and smaller companies may be more volatile than stocks of larger, more established companies, and may lack sufficient market liquidity. Mid-sized and small companies may have limited product lines or financial resources, may be dependent upon a particular niche of the market, or may be dependent upon a small or inexperienced management group. Securities of smaller companies may trade less frequently and in lower volume than the securities of larger companies, which could lead to higher transaction costs. Generally the smaller the company size, the greater the risk.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> <div style="margin-top: 6pt;">Valuation Risk is the risk that the sale price the Fund could receive for a portfolio security may differ from the Fund’s valuation of the security, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. In addition, the value of the securities in the Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year and (B) how the Fund’s average annual returns compare with those of a broad measure of market performance. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year and (B) how the Fund’s average annual returns compare with those of a broad measure of market performance. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the periods shown in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (6/30/2020): 21.62% </div> <div style="margin-top: 6pt;">Worst Quarter (3/31/2020): -31.00% </div> Best Quarter 2020-06-30 0.2162 Worst Quarter 2020-03-31 -0.3100 Average Annual Total Returns (for the periods ended December 31, 2024) -0.0853 0.0547 0.0506 -0.0915 0.0456 0.0426 -0.0445 0.0423 0.0392 0.1749 0.1006 0.0923 -0.0843 0.0597 0.0557 In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the Morningstar® Global Upstream Natural Resources IndexSM to the MSCI ACWI Index. The Fund will continue to compare its performance to the Morningstar® Global Upstream Natural Resources IndexSM, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® STOXX® Global Broad Infrastructure Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the STOXX® Global Broad Infrastructure Index (the “Underlying Index”).</div> Fees And Expenses Of The Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0047 0.0000 0.0001 0.0048 -0.0001 0.0047 March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 48 153 268 603 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 12% of the average value of its portfolio. 0.12 Principal Investment Strategies <div style="margin-top: 6pt;">The Underlying Index is designed to reflect the performance of a selection of companies that, in aggregate, offer broad exposure to publicly traded developed- and emerging-market infrastructure companies, including U.S. companies, as defined by STOXX Ltd. (the “Index Provider”) pursuant to its index methodology. In addition, NTI believes that the companies in the Underlying Index have the potential to generate income through dividend and other payments received. </div> <div style="margin-top: 6pt;">To be eligible for inclusion in the Underlying Index, companies must generate at least 50% of their respective revenues from the ownership, development, construction, financing or operation of infrastructure-related assets in the following five supersector groups: (i) communication (i.e., cable and satellite, data centers, wireless, wireless towers and wireline); (ii) energy (i.e., energy utilities and mid-stream energy); (iii) government outsourcing/social (i.e., correctional facilities, hospitals and postal services); (iv) transportation (i.e., air transportation, passenger transportation, rail transportation, road transportation and water transportation); and (v) utilities (i.e., waste management </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">and water utilities). Securities must also meet a certain minimum liquidity criteria: 3-month average daily trading volume (ADTV) greater than one million USD. Eligible securities are then selected based on largest free-float adjusted market capitalization, with a maximum of 40 securities from each supersector group and with a cap on the number of constituent securities among the sector groups of each supersector group. To prevent companies, supersectors and countries from dominating the portfolio, the Underlying Index also includes constituent, supersector and country weight caps (“Weight Caps”). Constituents of the Underlying Index may include common and preferred stocks, publicly-traded units of master limited partnerships (“MLPs”) and real estate investment trusts (“REITs”). </div> <div style="margin-top: 6pt;">As of December 31, 2024, the Underlying Index was comprised of 173 issues with market capitalizations ranging from $8.7 million to $67.5 billion. The Underlying Index is reconstituted on an annual basis and the Weight Caps are applied on a quarterly basis. The Fund generally reconstitutes or otherwise modifies its portfolio in accordance with the Underlying Index. </div> <div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. </div> <div style="margin-top: 6pt;">NTI uses a representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div> <div style="margin-top: 6pt;">Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index and in American Depositary Receipts (“ADRs”) and Global Depositary Receipts (“GDRs”) (collectively “Depositary Receipts”) based on the securities in the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">funds advised by NTI or its affiliates, futures contracts, options on futures contracts and forward currency contracts, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div> <div style="margin-top: 6pt;">The Underlying Index is sponsored by the Index Provider, an organization that is independent of the Fund and NTI. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div> <div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received). </div> <div style="margin-top: 6pt;">From time to time the Fund may focus its investments (i.e., invest more than 15% of its total assets) in one or more particular countries or geographic regions. As of December 31, 2024, the Fund focused its investments in Canada.</div> <div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in infrastructure-related companies in the communication, industrials and utilities subsector groups. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in infrastructure-related companies in the communication, industrials and utilities subsector groups. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time. Principal Risks <div style="margin-top: 6pt;">Equity Securities Risk is the risk that the values of the equity securities owned by the Fund may be more volatile and underperform other asset classes and the general securities markets.</div> <div style="margin-top: 6pt;">Mid Cap Stock Risk is the risk that stocks of mid-sized companies may be subject to more abrupt or erratic market movements than stocks of larger, more established companies, and may lack sufficient market liquidity. Mid-sized companies may have limited product lines or financial resources, and may be dependent upon a particular niche of the market, or may be dependent upon a small or inexperienced management group. Securities of smaller companies may trade less frequently and in lower volume than the securities of larger companies, which could lead to higher transaction costs. Generally the smaller the company size, the greater the risk.</div> <div style="margin-top: 6pt;">REIT Risk is the risk that the Fund’s investments may be affected by factors affecting REITs and the real estate sector generally. Investing in REITs involves certain unique risks in addition to those risks associated with investing in the real estate industry in general. REITs whose underlying properties are concentrated in a particular industry or geographic region are also subject to risks affecting such industries and regions. REITs may have limited financial resources, may trade less frequently and in lower volume, engage in dilutive offerings or become more volatile than other securities. By investing in REITs through the Fund, a shareholder will bear expenses of the REITs in addition to expenses of the Fund. In addition, REITs could possibly fail to (i) qualify for favorable tax treatment under applicable tax law, or (ii) maintain their exemption from registration under the Investment Company Act of 1940.</div> <div style="margin-top: 6pt;">MLP Risk is the risk that accompanies an investment in MLP units. The risks of investing in an MLP are similar to those of investing in a partnership, including more flexible governance structures, which could result in less protection for investors, such as the Fund, than investments in a corporation. An investor in an MLP normally would not be liable for the debts of the MLP beyond the amount that the investor has contributed but may not be shielded from liability to the same extent that a shareholder of a corporation would be. MLPs are also subject to risks related to potential conflicts of interest between the MLP and the MLP’s general partner and cash flow risks. MLPs that concentrate in a particular industry or a particular geographic region are subject to risks associated with such industry or </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">region. MLPs may also be sensitive to changes in interest rates and during periods of interest rate volatility, limited capital markets access and/or low commodities pricing and may not provide attractive returns.</div> <div style="margin-top: 6pt;">MLP Tax Risk. An MLP is a public limited partnership or limited liability company taxed as a partnership under the Internal Revenue Code of 1986. MLPs taxed as partnerships do not pay U.S. federal income tax at the partnership level, subject to the application of certain partnership audit rules. A change in current tax law, or a change in the underlying business mix of a given MLP, however, could result in an MLP being classified as a corporation for U.S. federal income tax purposes, which would have the effect of reducing the amount of cash available for distribution by the MLP and, as a result, could result in a reduction of the value of the Fund’s investment (and the Fund), and, consequently, lower income.</div> <div style="margin-top: 6pt;">Foreign Securities Risk is the risk that investing in foreign (non-U.S.) securities may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies, due to less liquid markets and adverse economic, political, diplomatic, financial, and regulatory factors. Foreign governments may impose limitations on foreigners’ ownership of interests in local issuers, restrictions on the ability to repatriate assets, and may also impose taxes. Any of these events could cause the value of the Fund’s investments to decline. Foreign banks, agents and securities depositories that hold the Fund’s foreign assets may be subject to little or no regulatory oversight over, or independent evaluation, of their operations. Additional costs associated with investments in foreign securities may include higher custodial fees than those applicable to domestic custodial arrangements and transaction costs of foreign currency conversions. Unless the Fund has hedged its foreign currency exposure, foreign securities risk also involves the risk of negative foreign currency rate fluctuations, which may cause the value of securities denominated in such foreign currency (or other instruments through which the Fund has exposure to foreign currencies) to decline in value. Currency exchange rates may fluctuate significantly over short periods of time. Currency hedging strategies, if used, are not always successful. For instance, forward foreign currency exchange contracts, if used by the Fund, could reduce performance if there are unanticipated changes in currency exchange rates.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Emerging Markets Risk is the risk that emerging markets are generally subject to greater market volatility, political, social and economic instability, uncertain trading markets and more governmental limitations on foreign investments than more developed markets. In addition, companies operating in emerging markets may be subject to lower trading volumes and greater price volatility than companies in more developed markets. Emerging market economies may be based on only a few industries, may be highly vulnerable to changes in local and global trade conditions, and may suffer from extreme and volatile debt burdens or inflation rates. Companies in emerging market countries generally may be subject to less stringent regulatory, disclosure, financial reporting, accounting, auditing and recordkeeping standards than companies in more developed countries. As a result, information, including financial information, about such companies may be less available and reliable, which can impede the Fund’s ability to evaluate such companies. Securities law and the enforcement of systems of taxation in many emerging market countries may change quickly and unpredictably, and the ability to bring and enforce actions (including bankruptcy, confiscatory taxation, expropriation, nationalization of a company’s assets, restrictions on foreign ownership of local companies, restrictions on withdrawing assets from the country, protectionist measures and practices such as share blocking), or to obtain information needed to pursue or enforce such actions, may be limited. Investments in emerging market securities may be subject to additional transaction costs, delays in settlement procedures, unexpected market closures, and lack of timely information.</div> <div style="margin-top: 6pt;">Depositary Receipts Risk. Foreign securities may trade in the form of depositary receipts. In addition to investment risks associated with the underlying issuer, depositary receipts may expose the Fund to additional risks associated with non-uniform terms that apply to depositary receipt programs, including credit exposure to the depository bank and to the sponsors and other parties with whom the depository bank establishes the programs, currency, political, economic, market risks and the risks of an illiquid market for depositary receipts. Depositary receipts are generally subject to the same risks as the foreign securities that they evidence or into which they may be converted. Depositary receipts may not track the price of the underlying foreign securities on which they are based, may have limited voting </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">rights, and may have a distribution subject to a fee charged by the depository. As a result, equity shares of the underlying issuer may trade at a discount or premium to the market price of the depositary receipts.</div> <div style="margin-top: 6pt;">Geographic Risk is the risk that if the Fund invests a significant portion of its total assets in certain issuers within the same country or geographic region, an adverse economic, business or political development affecting that country or region may affect the value of the Fund’s investments more, and the Fund’s investments may be more volatile, than if the Fund’s investments were not so concentrated in such country or region.</div> •Canada Investment Risk is the risk that the Fund is particularly sensitive to political, economic and social conditions in affecting Canada. The Canadian economy is especially dependent on the demand for, and supply of, natural resources, and the Canadian market is relatively concentrated in issuers involved in the production and distribution of natural resources, particularly the production of metals. Any adverse events that affect Canada’s major industries may have a negative impact on the overall Canadian economy and the Fund. <div style="margin-top: 6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase. </div> <div style="margin-top: 6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="margin-top: 6pt;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting. This risk may be heightened because of its investments in non-U.S. securities.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> •Infrastructure-Related CompaniesRisk is the risk that the Fund is subject to the risks associated with investment in infrastructure-related companies in addition to the general risk of the stock market. Risks associated with infrastructure-related companies include: (a) realized <div style="line-height: 12.10pt; margin-left: 14.97pt; margin-top: 0.00pt; text-align: left;"> revenue volume may be significantly lower than projected and/or there will be cost overruns; (b) infrastructure project sponsors will alter their terms making a project no longer economical; (c) macroeconomic factors such as low gross domestic product (“GDP”) growth or high nominal interest rates will raise the average cost of infrastructure funding; (d) government regulation may affect rates charged to infrastructure customers; (e) government budgetary constraints will impact infrastructure projects; (f) special tariffs will be imposed; and (g) changes in tax laws, regulatory policies or accounting standards could be unfavorable. Other risks include environmental damage due to a company’s operations or an accident, a natural disaster, changes in market sentiment towards infrastructure and terrorist acts. Any of these events could cause the value of the Fund’s or Underlying Fund’s investments in infrastructure-related companies to decline.</div> <div style="margin-top: 6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div> •Forward Foreign Currency Contracts Risk is the risk that, if forward prices increase, a loss will occur to the extent that the agreed upon purchase price of the currency exceeds the price of the currency that was agreed to be sold.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies.•Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss. <div style="margin-top: 6pt;">Interest Rate Risk is the risk that during periods of rising interest rates, the Fund’s yield (and the market value of its securities) will tend to be lower than prevailing market rates; in periods of falling interest rates, the Fund’s yield (and the market value of its securities) will tend to be higher. Increases in interest rates typically lower the present value of a REIT’s future earnings stream, and may make financing property purchases and improvements more costly. Because the market price of REIT stocks may change based upon investors’ collective perceptions of future earnings, the value of the Fund may decline when investors anticipate or experience rising interest rates. </div> <div style="margin-top: 6pt;">In general, securities with longer maturities or durations are more sensitive to interest rate changes. Changing interest rates, including rates that fall below zero, may have unpredictable effects on the markets and the Fund’s investments, may result in heightened market volatility, may impact the liquidity of fixed-income securities and of the Fund, and may detract from Fund performance. A low or negative interest rate environment could cause the Fund’s earnings to fall below the Fund’s expense ratio, resulting in a low or negative yield and a decline in the Fund’s NAV. A general rise in interest rates may cause investors to move out of fixed income securities on a large scale, which could adversely affect the price and liquidity of fixed income securities and could also result in increased redemptions for the Fund. During periods when inflation rates are high or rising, or during periods of low interest rates, the Fund may be subject to a greater risk of rising interest rates.</div> <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> <div style="margin-top: 6pt;">Valuation Risk is the risk that the sale price the Fund could receive for a portfolio security may differ from the Fund’s valuation of the security, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. In addition, the value of the securities in the Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year and (B) how the Fund’s average annual returns compare with those of a broad measure of market performance. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year and (B) how the Fund’s average annual returns compare with those of a broad measure of market performance. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the period shown in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (3/31/2019): 13.57% </div> <div style="margin-top: 6pt;">Worst Quarter (3/31/2020): -19.69%</div> Best Quarter 2019-03-31 0.1357 Worst Quarter 2020-03-31 -0.1969 Average Annual Total Returns (for the periods ended December 31, 2024) 0.0464 0.0287 0.0462 0.0370 0.0220 0.0394 0.0319 0.0215 0.0355 0.1749 0.1006 0.0923 0.0451 0.0275 0.0448 In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the STOXX® Global Broad Infrastructure Index to the MSCI ACWI Index. The Fund will continue to compare its performance to the STOXX® Global Broad Infrastructure Index, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® Global Quality Real Estate Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Northern Trust Global Quality Real Estate IndexSM (the “Underlying Index”).</div> Fees And Expenses Of The Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0045 0.0000 0.0001 0.0046 -0.0001 0.0045 March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 46 147 257 578 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 49% of the average value of its portfolio. 0.49 Principal Investment Strategies <div style="margin-top: 6pt;">The Underlying Index is designed to reflect the performance of a selection of companies that, in aggregate, maximize exposure to quality, value and momentum factors, within a universe of companies operating in the real estate sector. In order to be eligible for inclusion in the Underlying Index, a security must be a constituent of the Northern Trust Global Real Estate Index (the “Parent Index”), a float-adjusted market-capitalization weighted index of publicly-traded equity securities of U.S. and non-U.S. real estate investment trusts (REITs) and real estate operating companies. In addition, the Underlying Index utilizes the proprietary Northern Trust quality factor to identify companies that exhibit strength in profitability, management expertise and cash flow, while value and momentum factors are included to help provide long term capital appreciation and also mitigate risk. </div> <div style="margin-top: 6pt;">To derive the Underlying Index, NTI, acting in its capacity as index provider (the “Index Provider”), ranks all constituents of the Parent Index using a Northern Trust proprietary blended multi-factor score. This score is designed to measure companies based on the quantitative assess</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">ment of their respective (a) quality (i.e., a factor that seeks to identify companies that exhibit financial strength and stability relative to the Parent Index); (b) value (i.e., a factor reflecting the current worth a company relative to its own historical value, book value or valuation versus peers); and (c) momentum (i.e., a factor that reflects market sentiment and changes in security price over a given time period). The Index Provider then uses an optimization process to select and weight eligible securities in order to maximize the overall blended multi-factor score relative to the Parent Index. The optimization also includes industry group, region, country, style factor, single-security weight, liquidity and turnover constraints so that these index characteristics vary within acceptable bands relative to the Parent Index. A company must meet the following criteria to be eligible for inclusion in the Underlying Index: (a) a constituent of the Parent Index; and (b) it must be classified under the business sector of “Real Estate” by Refinitiv Business Classification or have registered as a real estate investment trust under its applicable local tax code. Companies classified under the business activities of Mortgage REITs and Real Estate Services (NEC) by Refinitiv Business Classification are excluded from the Underlying Index. The Underlying Index is reconstituted on a quarterly basis. The Fund generally reconstitutes its portfolio in accordance with the Underlying Index. </div> <div style="margin-top: 6pt;">As of December 31, 2024, the Underlying Index was comprised of 140 issues with market capitalizations ranging from $493.9 million to $100.8 billion. </div> <div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. </div> <div style="margin-top: 6pt;">NTI uses a representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index and in American Depositary Receipts (“ADRs”) and Global Depositary Receipts (“GDRs”) (collectively “Depositary Receipts”) based on the securities in the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts, options on futures contracts and forward currency contracts, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div> <div style="margin-top: 6pt;">The Underlying Index is created and sponsored by NTI, as the Index Provider. NTI also serves as the investment adviser to the Fund. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div> <div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received). </div> <div style="margin-top: 6pt;">From time to time the Fund may focus its investments (i.e., invest more than 15% of its total assets) in one or more particular countries or geographic regions.</div> <div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the real estate sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the real estate sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time. Principal Risks <div style="margin-top: 6pt;">Real Estate Securities Risk is the risk that the Fund is subject to the risks associated with investment in the real estate sector in addition to the general risk of the stock market. Investing in securities of real estate companies will make the Fund more susceptible to risks associated with the ownership of real estate and with the real estate industry in general, as well as risks that relate specifically to the way in which real estate companies are organized and operated. Real estate companies may have lower trading volumes and may be subject to more abrupt or erratic price movements than the overall securities markets. The value of real estate securities may underperform other sectors of the economy or broader equity markets. To the extent that the Fund concentrates its investments in the real estate sector, it may be subject to greater risk of loss than if it were diversified across different industry sectors.</div> <div style="margin-top: 6pt;">REIT Risk is the risk that the Fund’s investments may be affected by factors affecting REITs and the real estate sector generally. Investing in REITs involves certain unique risks in addition to those risks associated with investing in the real estate industry in general. REITs whose underlying properties are concentrated in a particular industry or geographic region are also subject to risks affecting such industries and regions. REITs may have limited financial resources, may trade less frequently and in lower volume, engage in dilutive offerings or become more volatile than other securities. By investing in REITs through the Fund, a shareholder will bear expenses of the REITs in addition to expenses of the Fund. In addition, REITs could possibly fail to (i) qualify for favorable tax treatment under applicable tax law, or (ii) maintain their exemption from registration under the Investment Company Act of 1940.</div> <div style="margin-top: 6pt;">Equity Securities Risk is the risk that the values of the equity securities owned by the Fund may be more volatile and underperform other asset classes and the general securities markets.</div> <div style="margin-top: 6pt;">Mid and Small Cap Stock Risk is the risk that stocks of mid-sized and smaller companies may be more volatile than stocks of larger, more established companies, and may </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">lack sufficient market liquidity. Mid-sized and small companies may have limited product lines or financial resources, may be dependent upon a particular niche of the market, or may be dependent upon a small or inexperienced management group. Securities of smaller companies may trade less frequently and in lower volume than the securities of larger companies, which could lead to higher transaction costs. Generally the smaller the company size, the greater the risk.</div> <div style="margin-top: 6pt;">Foreign Securities Risk is the risk that investing in foreign (non-U.S.) securities may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies, due to less liquid markets and adverse economic, political, diplomatic, financial, and regulatory factors. Foreign governments may impose limitations on foreigners’ ownership of interests in local issuers, restrictions on the ability to repatriate assets, and may also impose taxes. Any of these events could cause the value of the Fund’s investments to decline. Foreign banks, agents and securities depositories that hold the Fund’s foreign assets may be subject to little or no regulatory oversight over, or independent evaluation, of their operations. Additional costs associated with investments in foreign securities may include higher custodial fees than those applicable to domestic custodial arrangements and transaction costs of foreign currency conversions. Unless the Fund has hedged its foreign currency exposure, foreign securities risk also involves the risk of negative foreign currency rate fluctuations, which may cause the value of securities denominated in such foreign currency (or other instruments through which the Fund has exposure to foreign currencies) to decline in value. Currency exchange rates may fluctuate significantly over short periods of time. Currency hedging strategies, if used, are not always successful. For instance, forward foreign currency exchange contracts, if used by the Fund, could reduce performance if there are unanticipated changes in currency exchange rates.</div> <div style="margin-top: 6pt;">Geographic Risk is the risk that if the Fund invests a significant portion of its total assets in certain issuers within the same country or geographic region, an adverse economic, business or political development affecting that country or region may affect the value of the Fund’s investments more, and the Fund’s investments may be more volatile, than if the Fund’s investments were not so concentrated in such country or region.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase. </div> <div style="margin-top: 6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Momentum Risk is the risk that securities that have had higher recent price performance compared to other securities may be more volatile than a broad cross-section of securities or that returns on securities that have previously exhibited price momentum are less than returns on other securities or the overall stock market. Momentum can turn quickly and cause significant variation from other types of investments.</div> <div style="margin-top: 6pt;">Value Investing Risk is the risk that the Fund’s investment in companies whose securities are believed to be undervalued, relative to their underlying profitability, will not appreciate in value as anticipated.</div> <div style="margin-top: 6pt;">Quality Factor Risk is the risk that the past performance of companies that have exhibited quality characteristics does not continue or the returns on securities issued by such companies may be less than returns from other styles of investing or the overall stock market. There may be periods when quality investing is out of favor and during which time the Fund's performance may suffer.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting. This risk may be heightened because of its investments in non-U.S. securities.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> <div style="margin-top: 6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div> •Forward Foreign Currency Contracts Risk is the risk that, if forward prices increase, a loss will occur to the extent that the agreed upon purchase price of the currency exceeds the price of the currency that was agreed to be sold.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies.•Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss. <div style="margin-top: 6pt;">Depositary Receipts Risk. Foreign securities may trade in the form of depositary receipts. In addition to investment risks associated with the underlying issuer, depositary receipts may expose the Fund to additional risks associated with non-uniform terms that apply to depositary receipt programs, including credit exposure to the depository bank and to the sponsors and other parties with whom the depository bank establishes the programs, currency, political, economic, market risks and the risks of an illiquid market for depositary receipts. Depositary receipts are generally subject to the same risks as the foreign securities that they evidence or into which they may be converted. Depositary receipts may not track the price of the underlying foreign securities on which they are based, may have limited voting rights, and may have a distribution subject to a fee charged by the depository. As a result, equity shares of the underlying issuer may trade at a discount or premium to the market price of the depositary receipts.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Interest Rate Risk is the risk that during periods of rising interest rates, the Fund’s yield (and the market value of its securities) will tend to be lower than prevailing market rates; in periods of falling interest rates, the Fund’s yield (and the market value of its securities) will tend to be higher. Increases in interest rates typically lower the present value of a REIT’s future earnings stream, and may make financing property purchases and improvements more costly. Because the market price of REIT stocks may change based upon investors’ collective perceptions of future earnings, the value of the Fund may decline when investors anticipate or experience rising interest rates. </div> <div style="margin-top: 6pt;">In general, securities with longer maturities or durations are more sensitive to interest rate changes. Changing interest rates, including rates that fall below zero, may have unpredictable effects on the markets and the Fund’s investments, may result in heightened market volatility, may impact the liquidity of fixed-income securities and of the Fund, and may detract from Fund performance. A low or negative interest rate environment could cause the Fund’s earnings to fall below the Fund’s expense ratio, resulting in a low or negative yield and a decline in the Fund’s NAV. A general rise in interest rates may cause investors to move out of fixed income securities on a large scale, which could adversely affect the price and liquidity of fixed income securities and could also result in increased redemptions for the Fund. During periods when inflation rates are high or rising, or during periods of low interest rates, the Fund may be subject to a greater risk of rising interest rates.</div> <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> <div style="margin-top: 6pt;">Valuation Risk is the risk that the sale price the Fund could receive for a portfolio security may differ from the Fund’s valuation of the security, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. In addition, the value of the securities in the Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the period shown in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (3/31/2019): 15.40% </div> <div style="margin-top: 6pt;">Worst Quarter (3/31/2020): -26.72% </div> Best Quarter 2019-03-31 0.1540 Worst Quarter 2020-03-31 -0.2672 Average Annual Total Returns (for the periods ended December 31, 2024) 0.0561 0.0024 0.0319 0.0418 -0.0072 0.0209 0.0348 -0.0014 0.0206 0.1867 0.1116 0.0995 0.0094 -0.0100 0.0223 0.0561 0.0003 0.0305 In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the FTSE EPRA/NAREIT Developed IndexSM to the MSCI World Index. The Fund will continue to compare its performance to the FTSE EPRA/NAREIT Developed IndexSM, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® Real Assets Allocation Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Northern Trust Real Assets Allocation IndexSM (the “Underlying Index”).</div> Fees And Expenses Of The Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following other expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0049 0.0000 0.0001 0.0048 0.0098 -0.0047 0.0051 The “Total Annual Fund Operating Expenses” may not correlate to the ratio of expenses to average net assets as reported in the "Financial Highlights" section of the Prospectus, which reflects the operating expenses of the Fund and does not include “Acquired Fund Fees and Expenses.” March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 52 265 496 1159 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 28% of the average value of its portfolio. 0.28 Principal Investment Strategies <div style="margin-top: 6pt;">The Fund is a fund of funds and seeks its investment objective by investing primarily in the shares of other FlexShares® ETFs (each an “Underlying Fund” and together, the “Underlying Funds”) that are eligible for inclusion in the Underlying Index and listed below, rather than in securities of individual companies. The Underlying Funds themselves seek investment results corresponding to their own respective underlying indexes. The Underlying Funds invest primarily in separate sets of securities representing or providing exposures to global “real assets.” Real assets are defined by NTI, acting in its capacity as index provider (the “Index Provider”), as physical or tangible assets. Examples of real assets include but are not limited to </div> <div style="line-height: 11.90pt; margin-top: 0.00pt; text-align: left;">commodities, precious metals, oil, and real estate. Each Underlying Fund has its own risk profile and will contribute differently to the overall risk profile of the Fund. Each of the Underlying Funds invests in equity securities that are traded in or are issued by companies domiciled in global developed or emerging markets (including the U.S.). Certain of the Underlying Funds may invest in publicly-traded units of master limited partnerships (“MLPs”) and real estate investment trusts (“REITs”). </div> <div style="margin-top: 6pt;">The Underlying Index is designed to reflect the performance of an optimized allocation to the Underlying Funds that is intended to provide exposures to certain real assets and minimize overall volatility of investment in the Underlying Funds. </div> <div style="margin-top: 6pt;">As of December 31, 2024, the Underlying Index was comprised of the following Underlying Funds, each of which invests primarily in equity securities: a 50.05% weight to FlexShares® STOXX® Global Broad Infrastructure Index Fund, a 9.76% weight to FlexShares® Morningstar Global Upstream Natural Resources Index Fund and a 40.19% weight to FlexShares® Global Quality Real Estate Index Fund. The Underlying Index was constituted and is rebalanced at least annually using a rules-based methodology. The Underlying Index may be rebalanced semi-annually if the volatility of investment in the Underlying Funds surpasses a minimum threshold. The weights of each Underlying Fund, and the degree to which each Underlying Fund represents exposure to certain real assets, may change over time as the Underlying Index and the underlying indexes of the Underlying Funds are reconstituted and/or rebalanced (which may be quarterly) and their component securities fluctuate in value. The Fund generally reconstitutes and/or rebalances its portfolio in accordance with the Underlying Index. </div> <div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. </div> <div style="margin-top: 6pt;">NTI generally intends to replicate the constituent securities of the Fund’s Underlying Index. “Replication” is an indexing strategy in which a fund invests in substantially all of the securities in its underlying index in approximately the same proportions as in the underlying index. NTI may use a “representative sampling” strategy in certain circumstances, such as when it may not be possible or practicable to fully implement a replication strategy. Representative sampling is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. </div> <div style="line-height: 11.90pt; margin-top: 0.00pt; text-align: left;">Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts and options on futures contracts, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div> <div style="margin-top: 6pt;">The Underlying Index is created and sponsored by NTI. NTI also serves as the investment adviser to the Fund and the Underlying Funds. NTI, as the Index Provider, determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div> <div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received). </div> <div style="margin-top: 6pt;">From time to time the Fund may focus its investments (i.e., invest more than 15% of its total assets) in one or more particular countries or geographic regions. </div> <div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in real assets-related companies in the real estate, natural resources and infrastructure sectors. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in real assets-related companies in the real estate, natural resources and infrastructure sectors. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time. Principal Risks <div style="line-height: 11.90pt; margin-top: 0.00pt; text-align: left;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> •Real Estate Securities Risk is the risk that the Fund is subject to the risks associated with investment in the real estate sector in addition to the general risk of the stock market. Investing in securities of real estate companies will make the Fund more susceptible to risks associated with the ownership of real estate and with the real estate industry in general, as well as risks that relate specifically to the way in which real estate companies are organized and operated. Real estate companies may have lower trading volumes and may be subject to more abrupt or erratic price movements than the overall securities markets. The value of real estate securities may underperform other sectors of the economy or broader equity markets. To the extent that the Fund concentrates its investments in the real estate sector, it may be subject to greater risk of loss than if it were diversified across different industry sectors.•Natural Resources Sector Risk is the risk that the Fund is subject to the risks associated with investment in companies within the natural resources sector in addition to the general risk of the stock market. Companies within the natural resources sector can be significantly affected by events relating to U.S. and foreign political and economic developments and environmental and other government regulations, as well as other factors including, but not limited to: commodity price volatility, technological developments and natural or man-made disasters. Declines in the demand for, or prices of, natural resources generally would be expected to contribute to declines in the value of the Fund’s or Underlying Fund’s equity securities. Such declines may occur quickly and without warning and may negatively impact the value of the Fund and your investment.•Infrastructure-Related CompaniesRisk is the risk that the Fund is subject to the risks associated with investment in infrastructure-related companies in addition to the general risk of the stock market. Risks associated with infrastructure-related companies include: (a) realized revenue volume may be significantly lower than projected and/or there will be cost overruns; (b) infrastructure project sponsors will alter their terms making a project no longer economical; (c) macroeconomic factors such as low gross domestic product (“GDP”) growth or high nominal interest rates will raise the average cost of infrastructure funding; (d) government regulation may affect rates charged to infrastructure customers; (e) government budgetary constraints will impact infrastructure projects; (f) special tariffs will be imposed; and (g) changes in tax laws, regulatory policies or accounting standards could be unfavorable. Other risks include environmental damage due to a company’s operations or an accident, a natural disaster, changes in market sentiment towards infrastructure and terrorist acts. Any of these events could cause the value of the Fund’s or Underlying Fund’s investments in infrastructure-related companies to decline. <div style="margin-top: 6pt;">MLP Risk is the risk that accompanies an investment in MLP units. The risks of investing in an MLP are similar to those of investing in a partnership, including more flexible governance structures, which could result in less protection for investors, such as the Fund, than investments in a corporation. An investor in an MLP normally would not be liable for the debts of the MLP beyond the amount that the investor has contributed but may not be shielded from liability to the same extent that a shareholder of a corporation would be. MLPs are also subject to risks related to potential conflicts of interest between the MLP and the MLP’s general partner and cash flow risks. MLPs that concentrate in a particular industry or a particular geographic region are subject to risks associated with such industry or region. MLPs may also be sensitive to changes in interest rates and during periods of interest rate volatility, limited capital markets access and/or low commodities pricing and may not provide attractive returns.</div> <div style="margin-top: 6pt;">MLP Tax Risk. An MLP is a public limited partnership or limited liability company taxed as a partnership under the Internal Revenue Code of 1986. MLPs taxed as partnerships do not pay U.S. federal income tax at the partnership level, subject to the application of certain partnership audit rules. A change in current tax law, or a change in the underlying business mix of a given MLP, however, could result in an MLP being classified as a corporation for U.S. federal income tax purposes, which would have the effect of reducing the amount of cash available for distribution by the MLP and, as a result, could result in a reduction of the value of the Fund’s investment (and the Fund), and, consequently, lower income.</div> <div style="margin-top: 6pt;">Real Estate Securities Risk is the risk that the Fund or an Underlying Fund is subject to the risks associated with investment in the real estate sector in addition to the general risk of the stock market. Investing in securities of real estate companies will make an Underlying Fund, and the </div> <div style="line-height: 11.90pt; margin-top: 0.00pt; text-align: left;">Fund, more susceptible to risks associated with the ownership of real estate and with the real estate industry in general, as well as risks that relate specifically to the way in which real estate companies are organized and operated. Real estate companies may have lower trading volumes and may be subject to more abrupt or erratic price movements than the overall securities markets. The value of real estate securities may underperform other sectors of the economy or broader equity markets. To the extent that an Underlying Fund, and the Fund, concentrates its investments in the real estate sector, it may be subject to greater risk of loss than if it were diversified across different industry sectors.</div> <div style="margin-top: 6pt;">REIT Risk is the risk that the Fund’s investments may be affected by factors affecting REITs and the real estate sector generally. Investing in REITs involves certain unique risks in addition to those risks associated with investing in the real estate industry in general. REITs whose underlying properties are concentrated in a particular industry or geographic region are also subject to risks affecting such industries and regions. REITs may have limited financial resources, may trade less frequently and in lower volume, engage in dilutive offerings or become more volatile than other securities. By investing in REITs through the Fund, a shareholder will bear expenses of the REITs in addition to expenses of the Fund. In addition, REITs could possibly fail to (i) qualify for favorable tax treatment under applicable tax law, or (ii) maintain their exemption from registration under the Investment Company Act of 1940.</div> <div style="margin-top: 6pt;">Equity Securities Risk is the risk that the values of the equity securities owned by the Fund may be more volatile and underperform other asset classes and the general securities markets.</div> <div style="margin-top: 6pt;">Fund of Funds Risk is the risk that the Fund’s investment performance largely depends on the investment performance of the Underlying Funds in which it primarily invests. The Fund’s NAV will change with changes in the value of the Underlying Funds and other securities in which the Fund invests based on their market valuations. An investment of the Fund is subject to the risks associated with the Underlying Funds that comprise the Underlying Index. There is the risk that the Index Provider’s evaluations and assumptions regarding the asset classes represented by the Underlying Funds in the Underlying Index at any given time may be incorrect based on actual market conditions. </div> <div style="margin-top: 6pt;">An investment in the Fund will entail more costs and expenses than direct investments in the Underlying Funds. The Fund will indirectly pay a proportional share of the </div> <div style="line-height: 11.90pt; margin-top: 0.00pt; text-align: left;">expenses of the Underlying Funds in which it invests (including operating expenses and management fees), in addition to the fees and expenses it pays directly. As the Fund’s allocation to the Underlying Funds changes from time to time, or to the extent that the expense ratio of the Underlying Funds changes, the weighted average operating expenses borne by the Fund may increase or decrease.</div> <div style="margin-top: 6pt;">Tax Risk is the risk that, because the Fund invests in the Underlying Funds, the Fund’s realized losses on sales of shares of the Underlying Funds may be indefinitely or permanently deferred as “wash sales.” Distributions of short-term capital gains by the Underlying Funds will be recognized as ordinary income by the Fund and would not be offset by the Fund’s capital loss carryforwards, if any. Capital loss carryforwards of the Underlying Funds, if any, would not offset net capital gains of the Fund. Each of these effects is caused by the Fund’s investment in the Underlying Funds and may result in distributions to Fund shareholders being of higher magnitudes and less likely to qualify for lower capital gain tax rates than if the Fund were to invest otherwise.</div> <div style="margin-top: 6pt;">Model Risk is the risk that the asset allocation model used to calculate the Underlying Index will not achieve its intended results.</div> <div style="margin-top: 6pt;">Momentum Risk is the risk that securities that have had higher recent price performance compared to other securities may be more volatile than a broad cross-section of securities or that returns on securities that have previously exhibited price momentum are less than returns on other securities or the overall stock market. Momentum can turn quickly and cause significant variation from other types of investments. An Underlying Fund may follow an index that selects constituent securities based on a “momentum” factor.</div> <div style="margin-top: 6pt;">Value Investing Risk is the risk that an Underlying Fund’s investment in companies whose securities are believed to be undervalued, relative to their underlying profitability, will not appreciate in value as anticipated.</div> <div style="margin-top: 6pt;">Quality Factor Risk is the risk that the past performance of companies that have exhibited quality characteristics does not continue or the returns on securities issued by such companies may be less than returns from other styles of investing or the overall stock market. There may be periods when quality investing is out of favor and during which time the Fund's performance may suffer.</div> <div style="margin-top: 6pt;">Foreign Securities Risk is the risk that investing in foreign (non-U.S.) securities may result in the Fund experiencing more rapid and extreme changes in value than a fund that </div> <div style="line-height: 11.90pt; margin-top: 0.00pt; text-align: left;">invests exclusively in securities of U.S. companies, due to less liquid markets and adverse economic, political, diplomatic, financial, and regulatory factors. Foreign governments may impose limitations on foreigners’ ownership of interests in local issuers, restrictions on the ability to repatriate assets, and may also impose taxes. Any of these events could cause the value of the Fund’s investments to decline. Foreign banks, agents and securities depositories that hold the Fund’s foreign assets may be subject to little or no regulatory oversight over, or independent evaluation, of their operations. Additional costs associated with investments in foreign securities may include higher custodial fees than those applicable to domestic custodial arrangements and transaction costs of foreign currency conversions. Unless the Fund has hedged its foreign currency exposure, foreign securities risk also involves the risk of negative foreign currency rate fluctuations, which may cause the value of securities denominated in such foreign currency (or other instruments through which the Fund has exposure to foreign currencies) to decline in value. Currency exchange rates may fluctuate significantly over short periods of time. Currency hedging strategies, if used, are not always successful. For instance, forward foreign currency exchange contracts, if used by the Fund, could reduce performance if there are unanticipated changes in currency exchange rates.</div> <div style="margin-top: 6pt;">Emerging Markets Risk is the risk that emerging markets are generally subject to greater market volatility, political, social and economic instability, uncertain trading markets and more governmental limitations on foreign investments than more developed markets. In addition, companies operating in emerging markets may be subject to lower trading volumes and greater price volatility than companies in more developed markets. Emerging market economies may be based on only a few industries, may be highly vulnerable to changes in local and global trade conditions, and may suffer from extreme and volatile debt burdens or inflation rates. Companies in emerging market countries generally may be subject to less stringent regulatory, disclosure, financial reporting, accounting, auditing and recordkeeping standards than companies in more developed countries. As a result, information, including financial information, about such companies may be less available and reliable, which can impede the Fund’s ability to evaluate such companies. Securities law and the enforcement of systems of taxation in many emerging market countries may change quickly and unpredictably, and the ability to bring and enforce actions (including bankruptcy, confiscatory taxation, expropriation, nationalization of a company’s assets, restrictions on foreign ownership of local </div> <div style="line-height: 11.90pt; margin-top: 0.00pt; text-align: left;">companies, restrictions on withdrawing assets from the country, protectionist measures and practices such as share blocking), or to obtain information needed to pursue or enforce such actions, may be limited. Investments in emerging market securities may be subject to additional transaction costs, delays in settlement procedures, unexpected market closures, and lack of timely information.</div> <div style="margin-top: 6pt;">Geographic Risk is the risk that if the Fund invests a significant portion of its total assets in certain issuers within the same country or geographic region, an adverse economic, business or political development affecting that country or region may affect the value of the Fund’s investments more, and the Fund’s investments may be more volatile, than if the Fund’s investments were not so concentrated in such country or region.</div> <div style="margin-top: 6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase.</div> <div style="margin-top: 6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, trans</div> <div style="line-height: 11.90pt; margin-top: 0.00pt; text-align: left;">action costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund and the Underlying Funds face because their shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund or Underlying Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with </div> <div style="line-height: 11.90pt; margin-top: 0.00pt; text-align: left;">changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top: 6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div> •Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies.•Forward Foreign Currency Contracts Risk is the risk that, if forward prices increase, a loss will occur to the extent that the agreed upon purchase price of the currency exceeds the price of the currency that was agreed to be sold. <div style="margin-top: 6pt;">Interest Rate Risk is the risk that during periods of rising interest rates, the Fund’s yield (and the market value of its securities) will tend to be lower than prevailing market </div> <div style="line-height: 11.90pt; margin-top: 0.00pt; text-align: left;">rates; in periods of falling interest rates, the Fund’s yield (and the market value of its securities) will tend to be higher. Increases in interest rates typically lower the present value of a REIT’s future earnings stream, and may make financing property purchases and improvements more costly. Because the market price of REIT stocks may change based upon investors’ collective perceptions of future earnings, the value of the Fund may decline when investors anticipate or experience rising interest rates. </div> <div style="margin-top: 6pt;">In general, securities with longer maturities or durations are more sensitive to interest rate changes. Changing interest rates, including rates that fall below zero, may have unpredictable effects on the markets and the Fund’s investments, may result in heightened market volatility, may impact the liquidity of fixed-income securities and of the Fund, and may detract from Fund performance. A low or negative interest rate environment could cause the Fund’s earnings to fall below the Fund’s expense ratio, resulting in a low or negative yield and a decline in the Fund’s NAV. A general rise in interest rates may cause investors to move out of fixed income securities on a large scale, which could adversely affect the price and liquidity of fixed income securities and could also result in increased redemptions for the Fund. During periods when inflation rates are high or rising, or during periods of low interest rates, the Fund may be subject to a greater risk of rising interest rates.</div> <div style="margin-top: 6pt;">Mid and Small Cap Stock Risk is the risk that stocks of mid-sized and smaller companies may be more volatile than stocks of larger, more established companies, and may lack sufficient market liquidity. Mid-sized and small companies may have limited product lines or financial resources, may be dependent upon a particular niche of the market, or may be dependent upon a small or inexperienced management group. Securities of smaller companies may trade less frequently and in lower volume than the securities of larger companies, which could lead to higher transaction costs. Generally the smaller the company size, the greater the risk.</div> <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> <div style="margin-top: 6pt;">Valuation Risk is the risk that the sale price the Fund or an Underlying Fund could receive for a portfolio security may differ from the Fund’s or the Underlying Fund’s valuation </div> <div style="line-height: 11.90pt; margin-top: 0.00pt; text-align: left;">of the security, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. In addition, the value of the securities in the Fund’s or an Underlying Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the periods in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (3/31/2019): 14.27% </div> <div style="margin-top: 6pt;">Worst Quarter (3/31/2020): -23.50%</div> Best Quarter 2019-03-31 0.1427 Worst Quarter 2020-03-31 -0.2350 Average Annual Total Returns (for the periods ended December 31, 2024) 0.0066 0.0236 0.0498 2015-11-23 -0.0036 0.0158 0.0410 0.0085 0.0170 0.0372 0.1749 0.1006 0.1020 0.0072 0.0247 0.0510 Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® Quality Dividend Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Northern Trust Quality Dividend IndexSM (the “Underlying Index”).</div> Fees and Expenses of the Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0037 0.0000 0.0001 0.0038 -0.0001 0.0037 March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 38 121 212 479 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 38% of the average value of its portfolio. 0.38 Principal Investment Strategies <div style="margin-top: 6pt;">The Underlying Index is designed to reflect the performance of a selection of companies that, in aggregate, provide exposure to a high-quality income-oriented universe of long-only U.S. equity securities, with an emphasis on long-term capital growth and a targeted overall beta that is similar to that of the Northern Trust 1250 Index (the “Parent Index”), a float-adjusted market-capitalization weighted index of U.S. domiciled large- and mid-capitalization companies. Beta represents the market sensitivity, relative to a given market index and time period, and is one measure of volatility. </div> <div style="margin-top: 6pt;">To derive the Underlying Index, NTI, acting in its capacity as the index provider (the “Index Provider”), begins with all securities in the Parent Index and then removes those securities that rank in the lowest quintile of quality based on a proprietary scoring model, as well as those which do not pay a dividend. The core components of the proprietary quality scoring model are based on quantitative ranking of various metrics obtained from company filings. These scores have three components: (i) management efficiency (e.g., corporate finance activities); (ii) profitability </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">(e.g., reliability and sustainability of financial performance); and (iii) cash flow (e.g., cash flow generation). The Index Provider then uses an optimization process to select and weight eligible securities in order to (a) maximize the overall quality score relative to the Parent Index; (b) attain an aggregate dividend yield in excess of the Parent Index; and (c) achieve the desired beta target. The optimization process also includes sector, industry group, single-security weight, liquidity and turnover constraints to assist in reducing the Underlying Index’s overall active risk exposure to any one single factor. As of December 31, 2024, there were 143 issues in the Underlying Index. The Underlying Index is reconstituted quarterly. The Fund generally reconstitutes its portfolio in accordance with the Underlying Index. </div> <div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” its Underlying Index and does not seek temporary defensive positions when markets decline or appear overvalued. </div> <div style="margin-top: 6pt;">NTI uses a representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div> <div style="margin-top: 6pt;">Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts and options on futures contracts, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div> <div style="margin-top: 6pt;">The Underlying Index is created and sponsored by NTI, as the Index Provider. NTI also serves as the investment adviser to the Fund. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received).</div> <div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the Information Technology sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the Information Technology sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time. Principal Risks <div style="margin-top: 6pt;">Equity Securities Risk is the risk that the values of the equity securities owned by the Fund may be more volatile and underperform other asset classes and the general securities markets.</div> <div style="margin-top: 6pt;">Mid Cap Stock Risk is the risk that stocks of mid-sized companies may be subject to more abrupt or erratic market movements than stocks of larger, more established companies, and may lack sufficient market liquidity. Mid-sized companies may have limited product lines or financial resources, and may be dependent upon a particular niche of the market, or may be dependent upon a small or inexperienced management group. Securities of smaller companies may trade less frequently and in lower volume than the securities of larger companies, which could lead to higher transaction costs. Generally the smaller the company size, the greater the risk.</div> <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> •Information Technology Sector Risk is the risk that securities of technology companies may be subject to greater price volatility than securities of companies in other sectors. These securities may fall in and out of favor with investors rapidly, which may cause sudden selling and dramatically lower market prices. Technology securities also may be affected adversely by changes in technology, consumer and business purchasing patterns, government regulation and/or obsolete products or services. <div style="margin-top: 6pt;">Dividend Risk is the risk that an issuer of stock held by the Fund may choose not to declare a dividend or the dividend rate might not remain at current levels. Dividend paying stocks might not experience the same level of earnings growth or capital appreciation as non-dividend paying stocks. The Fund’s performance during a broad market advance could suffer because dividend paying stocks may not experience the same capital appreciation as non-dividend paying stocks. </div> <div style="margin-top: 6pt;">Volatility Risk is the risk that the actual level of volatility experienced by the Fund may be greater or lower than the targeted overall volatility of the Underlying Index. Although the Underlying Index is designed to have a targeted overall volatility that is similar to that of the Parent Index, there is no guarantee that it will have the targeted overall volatility. The Fund will continue to seek to track the Underlying Index even if the Underlying Index does not have the targeted overall volatility. There is also the risk that the Fund may experience volatility greater or lower than that of the Underlying Index as a result of tracking error. A portfolio of securities with greater volatility is generally considered to have a higher risk profile than a portfolio with lower volatility.</div> <div style="margin-top: 6pt;">Quality Factor Risk is the risk that the past performance of companies that have exhibited quality characteristics does not continue or the returns on securities issued by such companies may be less than returns from other styles of investing or the overall stock market. There may be periods when quality investing is out of favor and during which time the Fund's performance may suffer.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase. </div> <div style="margin-top: 6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top: 6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div> •Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies. <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the periods in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (6/30/2020): 18.51% </div> <div style="margin-top: 6pt;">Worst Quarter (3/31/2020): -25.18%</div> Best Quarter 2020-06-30 0.1851 Worst Quarter 2020-03-31 -0.2518 Average Annual Total Returns(for the periods ended December 31, 2024) 0.1694 0.1032 0.0992 0.1628 0.0964 0.0910 0.1029 0.0799 0.0785 0.2451 0.1427 0.1287 0.1733 0.1080 0.1043 Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® Quality Dividend Defensive Index Fund Investment Objective <div style="margin-top:6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Northern Trust Quality Dividend Defensive IndexSM (the “Underlying Index”).</div> Fees and Expenses of the Fund <div style="margin-top:6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0037 0.0000 0.0001 0.0038 -0.0001 0.0037 March 1, 2026 Example <div style="margin-top:6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The </div><div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 38 121 212 479 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 50% of the average value of its portfolio. 0.50 Principal Investment Strategies <div style="margin-top:6pt;">The Underlying Index is designed to reflect the performance of a selection of companies that, in aggregate, provide exposure to a high quality income-oriented universe of long-only U.S. equity securities, with an emphasis on long-term capital growth and a targeted overall beta that is generally between 0.5 to 1.0 times that of the Northern Trust 1250 Index (the “Parent Index”), a float-adjusted market-capitalization weighted index of U.S. domiciled large- and mid-capitalization companies. Beta represents the market sensitivity, relative to a given market index and time period, and is one measure of volatility. </div><div style="margin-top:6pt;">To derive the Underlying Index, NTI, acting in its capacity as the index provider (the “Index Provider”), begins with all securities in the Parent Index and then removes those securities that rank in the lowest quintile of quality based on a proprietary scoring model, as well as those which do not pay a dividend. The core components of the proprietary quality scoring model are based on quantitative ranking of various metrics obtained from company filings. These scores have three components: (i) management efficiency (e.g., corporate finance activities); (ii) profitability </div><div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">(e.g., reliability and sustainability of financial performance); and (iii) cash flow (e.g., cash flow generation). The Index Provider then uses an optimization process to select and weight eligible securities in order to (a) maximize the overall quality score relative to the Parent Index, (b) attain an aggregate dividend yield in excess of the Parent Index and (c) achieve the desired beta target. The optimization process also includes sector, industry group, single-security weight, liquidity and turnover constraints to assist in reducing the Underlying Index’s overall active risk exposure to any one single factor. As of December 31, 2024, there were 128 issues in the Underlying Index. The Underlying Index is reconstituted quarterly. The Fund generally reconstitutes its portfolio in accordance with the Underlying Index. </div><div style="margin-top:6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” its Underlying Index and does not seek temporary defensive positions when markets decline or appear overvalued. </div><div style="margin-top:6pt;">NTI uses a representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div><div style="margin-top:6pt;">Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts and options on futures contracts, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div><div style="margin-top:6pt;">The Underlying Index is created and sponsored by NTI, as the Index Provider. NTI also serves as the investment adviser to the Fund. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div><div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received).</div><div style="margin-top:6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the Information Technology sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the Information Technology sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time. Principal Risks <div style="margin-top:6pt;">Equity Securities Risk is the risk that the values of the equity securities owned by the Fund may be more volatile and underperform other asset classes and the general securities markets.</div> <div style="margin-top:6pt;">Mid Cap Stock Risk is the risk that stocks of mid-sized companies may be subject to more abrupt or erratic market movements than stocks of larger, more established companies, and may lack sufficient market liquidity. Mid-sized companies may have limited product lines or financial resources, and may be dependent upon a particular niche of the market, or may be dependent upon a small or inexperienced management group. Securities of smaller companies may trade less frequently and in lower volume than the securities of larger companies, which could lead to higher transaction costs. Generally the smaller the company size, the greater the risk.</div> <div style="margin-top:6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is </div><div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div>•Information Technology Sector Risk is the risk that securities of technology companies may be subject to greater price volatility than securities of companies in other sectors. These securities may fall in and out of favor with investors rapidly, which may cause sudden selling and dramatically lower market prices. Technology securities also may be affected adversely by changes in technology, consumer and business purchasing patterns, government regulation and/or obsolete products or services. <div style="margin-top:6pt;">Dividend Risk is the risk that an issuer of stock held by the Fund may choose not to declare a dividend or the dividend rate might not remain at current levels. Dividend paying stocks might not experience the same level of earnings growth or capital appreciation as non-dividend paying stocks. The Fund’s performance during a broad market advance could suffer because dividend paying stocks may not experience the same capital appreciation as non-dividend paying stocks. </div> <div style="margin-top:6pt;">Volatility Risk is the risk that the actual level of volatility experienced by the Fund may be greater or lower than the targeted overall volatility of the Underlying Index. Although the Underlying Index is designed to have a targeted overall volatility that is lower than that of the Parent Index, there is no guarantee that it will have the targeted overall volatility. The Fund will continue to seek to track the Underlying Index even if the Underlying Index does not have the targeted overall volatility. There is also the risk that the Fund may experience volatility greater or lower than that of the Underlying Index as a result of tracking error. A portfolio of securities with greater volatility is generally considered to have a higher risk profile than a portfolio with lower volatility.</div> <div style="margin-top:6pt;">Quality Factor Risk is the risk that the past performance of companies that have exhibited quality characteristics does not continue or the returns on securities issued by such companies may be less than returns from other styles of investing or the overall stock market. There may be periods when quality investing is out of favor and during which time the Fund's performance may suffer.</div> <div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase. </div> <div style="margin-top:6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top:6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top:6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting.</div> <div style="margin-top:6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top:6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div><div style="margin-top:6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices </div><div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top:6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div>•Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies. <div style="margin-top:6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The </div><div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top:6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top:6pt;">For the periods in the bar chart above: </div><div style="margin-top:6pt;">Best Quarter (6/30/2020): 15.95% </div><div style="margin-top:6pt;">Worst Quarter (3/31/2020): -23.37%</div> Best Quarter 2020-06-30 0.1595 Worst Quarter 2020-03-31 -0.2337 Average Annual Total Returns(for the periods ended December 31, 2024) 0.2132 0.1053 0.1031 0.2070 0.0991 0.0946 0.1292 0.0822 0.0819 0.2451 0.1427 0.1287 0.2163 0.1085 0.1088 Reflects no deduction for fees, expenses or taxes. <div style="margin-top:6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® International Quality Dividend Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Northern Trust International Quality Dividend IndexSM (the “Underlying Index”).</div> Fees and Expenses of the Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0047 0.0000 0.0002 0.0049 -0.0002 0.0047 March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 48 155 272 614 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 51% of the average value of its portfolio. 0.51 Principal Investment Strategies <div style="margin-top: 6pt;">The Underlying Index is designed to reflect the performance of a selection of companies that, in aggregate, provide exposure to a high-quality income-oriented universe of long-only international securities issued by non-U.S.- based companies, with an emphasis on long-term capital growth and a targeted overall beta that is similar to that of the Northern Trust International Large Cap Index (the “Parent Index”), a float-adjusted market-capitalization weighted index of non-US domiciled large- and mid-capitalization companies. Beta represents the market sensitivity, relative to a given market index and time period, and is one measure of volatility. </div> <div style="margin-top: 6pt;">To derive the Underlying Index, NTI, acting in its capacity as the index provider (the “Index Provider”), begins with all securities in the Parent Index that have an average daily traded value of at least $125,000 in the 90 days prior to a reconstitution, and then removes those securities that rank in the lowest quintile of quality based on a proprietary scoring model, as well as those which do not pay a dividend. The core components of the proprietary quality scoring model are based on quantitative ranking of various </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">metrics obtained from company filings. These scores have three components: (i) management efficiency (e.g., corporate finance activities); (ii) profitability (e.g., reliability and sustainability of financial performance); and (iii) cash flow (e.g., cash flow generation). The Index Provider then uses an optimization process to select and weight eligible securities in order to (a) maximize the overall quality score relative to the Parent Index; (b) attain an aggregate dividend yield in excess of the Parent Index; and (c) achieve the desired beta target. The optimization process also includes sector, industry group, region, country, single-security weight, liquidity and turnover constraints to assist in reducing the Underlying Index’s overall active risk exposure to any one single factor. As of December 31, 2024, there were 213 issues in the Underlying Index. The Underlying Index is reconstituted quarterly. The Fund generally reconstitutes its portfolio in accordance with the Underlying Index. </div> <div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” its Underlying Index and does not seek temporary defensive positions when markets decline or appear overvalued. </div> <div style="margin-top: 6pt;">NTI uses a representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div> <div style="margin-top: 6pt;">Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index and in American Depositary Receipts (“ADRs”) and Global Depositary Receipts (“GDRs”) (collectively “Depositary Receipts”) based on the securities in the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts, options on futures contracts and foreign currency contracts, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">The Underlying Index is created and sponsored by NTI, as the Index Provider. NTI also serves as the investment adviser to the Fund. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div> <div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received). </div> <div style="margin-top: 6pt;">From time to time the Fund may focus its investments (i.e., invest more than 15% of its total) in one or more particular countries or geographic regions. </div> <div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the financial sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the financial sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time. Principal Risks <div style="margin-top: 6pt;">Equity Securities Risk is the risk that the values of the equity securities owned by the Fund may be more volatile and underperform other asset classes and the general securities markets.</div> <div style="margin-top: 6pt;">Mid Cap Stock Risk is the risk that stocks of mid-sized companies may be subject to more abrupt or erratic market movements than stocks of larger, more established companies,</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;"> and may lack sufficient market liquidity. Mid-sized companies may have limited product lines or financial resources, and may be dependent upon a particular niche of the market, or may be dependent upon a small or inexperienced management group. Securities of smaller companies may trade less frequently and in lower volume than the securities of larger companies, which could lead to higher transaction costs. Generally the smaller the company size, the greater the risk.</div> <div style="margin-top: 6pt;">Foreign Securities Risk is the risk that investing in foreign (non-U.S.) securities may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies, due to less liquid markets and adverse economic, political, diplomatic, financial, and regulatory factors. Foreign governments may impose limitations on foreigners’ ownership of interests in local issuers, restrictions on the ability to repatriate assets, and may also impose taxes. Any of these events could cause the value of the Fund’s investments to decline. Foreign banks, agents and securities depositories that hold the Fund’s foreign assets may be subject to little or no regulatory oversight over, or independent evaluation, of their operations. Additional costs associated with investments in foreign securities may include higher custodial fees than those applicable to domestic custodial arrangements and transaction costs of foreign currency conversions. Unless the Fund has hedged its foreign currency exposure, foreign securities risk also involves the risk of negative foreign currency rate fluctuations, which may cause the value of securities denominated in such foreign currency (or other instruments through which the Fund has exposure to foreign currencies) to decline in value. Currency exchange rates may fluctuate significantly over short periods of time. Currency hedging strategies, if used, are not always successful. For instance, forward foreign currency exchange contracts, if used by the Fund, could reduce performance if there are unanticipated changes in currency exchange rates.</div> <div style="margin-top: 6pt;">Emerging Markets Risk is the risk that emerging markets are generally subject to greater market volatility, political, social and economic instability, uncertain trading markets and more governmental limitations on foreign investments than more developed markets. In addition, companies operating in emerging markets may be subject to lower trading volumes and greater price volatility than companies</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;"> in more developed markets. Emerging market economies may be based on only a few industries, may be highly vulnerable to changes in local and global trade conditions, and may suffer from extreme and volatile debt burdens or inflation rates. Companies in emerging market countries generally may be subject to less stringent regulatory, disclosure, financial reporting, accounting, auditing and recordkeeping standards than companies in more developed countries. As a result, information, including financial information, about such companies may be less available and reliable, which can impede the Fund’s ability to evaluate such companies. Securities law and the enforcement of systems of taxation in many emerging market countries may change quickly and unpredictably, and the ability to bring and enforce actions (including bankruptcy, confiscatory taxation, expropriation, nationalization of a company’s assets, restrictions on foreign ownership of local companies, restrictions on withdrawing assets from the country, protectionist measures and practices such as share blocking), or to obtain information needed to pursue or enforce such actions, may be limited. Investments in emerging market securities may be subject to additional transaction costs, delays in settlement procedures, unexpected market closures, and lack of timely information.</div> <div style="margin-top: 6pt;">Geographic Risk is the risk that if the Fund invests a significant portion of its total assets in certain issuers within the same country or geographic region, an adverse economic, business or political development affecting that country or region may affect the value of the Fund’s investments more, and the Fund’s investments may be more volatile, than if the Fund’s investments were not so concentrated in such country or region.</div> <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> •Financial Sector Risk is the risk that the financial sector can be significantly affected by changes in interest rates, government regulation, the rate of corporate and consumer debt defaulted, price competition, and the availability and cost of capital, among other factors. <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Dividend Risk is the risk that an issuer of stock held by the Fund may choose not to declare a dividend or the dividend rate might not remain at current levels. Dividend paying stocks might not experience the same level of earnings growth or capital appreciation as non-dividend paying stocks. The Fund’s performance during a broad market advance could suffer because dividend paying stocks may not experience the same capital appreciation as non-dividend paying stocks. </div> <div style="margin-top: 6pt;">Volatility Risk is the risk that the actual level of volatility experienced by the Fund may be greater or lower than the targeted overall volatility of the Underlying Index. Although the Underlying Index is designed to have a targeted overall volatility that is similar to that of the Parent Index, there is no guarantee that it will have the targeted overall volatility. The Fund will continue to seek to track the Underlying Index even if the Underlying Index does not have the targeted overall volatility. There is also the risk that the Fund may experience volatility greater or lower than that of the Underlying Index as a result of tracking error. A portfolio of securities with greater volatility is generally considered to have a higher risk profile than a portfolio with lower volatility.</div> <div style="margin-top: 6pt;">Quality Factor Risk is the risk that the past performance of companies that have exhibited quality characteristics does not continue or the returns on securities issued by such companies may be less than returns from other styles of investing or the overall stock market. There may be periods when quality investing is out of favor and during which time the Fund's performance may suffer.</div> <div style="margin-top: 6pt;">Depositary Receipts Risk Foreign securities may trade in the form of depositary receipts. In addition to investment risks associated with the underlying issuer, depositary receipts may expose the Fund to additional risks associated with non-uniform terms that apply to depositary receipt programs, including credit exposure to the depository bank and to the sponsors and other parties with whom the depository bank establishes the programs, currency, political, economic, market risks and the risks of an illiquid market for depositary receipts. Depositary receipts are generally subject to the same risks as the foreign securities that they evidence or into which they may be converted. Depositary receipts may not track the price of the underlying foreign securities on which they are based, may have limited voting </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">rights, and may have a distribution subject to a fee charged by the depository. As a result, equity shares of the underlying issuer may trade at a discount or premium to the market price of the depositary receipts.</div> <div style="margin-top: 6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase. </div> <div style="margin-top: 6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">its Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="margin-top: 6pt;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting. This risk may be heightened because of its investments in non-U.S. securities.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top: 6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div> •Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies.•Forward Foreign Currency Contracts Risk is the risk that, if forward prices increase, a loss will occur to the extent that the agreed upon purchase price of the currency exceeds the price of the currency that was agreed to be sold. <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> <div style="margin-top: 6pt;">Valuation Risk is the risk that the sale price the Fund could receive for a portfolio security may differ from the Fund’s valuation of the security, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. In addition, the value of the securities in the Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;"> indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the period shown in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (12/31/2020): 18.20% </div> <div style="margin-top: 6pt;">Worst Quarter (3/31/2020): -26.07%</div> Best Quarter 2020-12-31 0.1820 Worst Quarter 2020-03-31 -0.2607 Average Annual Total Returns(for the periods ended December 31, 2024) 0.0661 0.0445 0.0416 0.0487 0.0311 0.0296 0.0494 0.0326 0.0308 0.0553 0.0410 0.0480 0.0695 0.0486 0.0456 Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® International Quality Dividend Dynamic Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Northern Trust International Quality Dividend Dynamic IndexSM (the “Underlying Index”).</div> Fees and Expenses of the Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0047 0.0000 0.0004 0.0051 -0.0004 0.0047 March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 48 160 281 637 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 61% of the average value of its portfolio. 0.61 Principal Investment Strategies <div style="margin-top: 6pt;">The Underlying Index is designed to reflect the performance of a selection of companies that, in aggregate, provide exposure to a high-quality income-oriented universe of long-only international securities issued by non-U.S.-based companies, with an emphasis on long-term capital growth and a targeted overall beta that is generally between 1.0 to 1.5 times that of the Northern Trust International Large Cap Index (the “Parent Index”), a float-adjusted market-capitalization weighted index of non-US domiciled large- and mid-capitalization companies. Beta represents the market sensitivity, relative to a given market index and time period, and is one measure of volatility. </div> <div style="margin-top: 6pt;">To derive the Underlying Index, NTI, acting in its capacity as the index provider (the “Index Provider”), begins with all securities in the Parent Index that have an average daily traded value of at least $125,000 in the 90 days prior to a reconstitution, and then removes those securities that rank in the lowest quintile of quality based on a proprietary scoring model, as well as those which do not pay a dividend. The core components of the proprietary quality scoring model are based on quantitative ranking of various </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">metrics obtained from company filings. These scores have three components: (i) management efficiency (e.g., corporate finance activities); (ii) profitability (e.g., reliability and sustainability of financial performance); and (iii) cash flow (e.g., cash flow generation). The Index Provider then uses an optimization process to select and weight eligible securities in order to (a) maximize the overall quality score relative to the Parent Index, (b) attain an aggregate dividend yield in excess of the Parent Index and (c) achieve the desired beta target. The optimization process also includes sector, industry group, region, country, single-security weight, liquidity and turnover constraints to assist in reducing the Underlying Index’s overall active risk exposure to any one single factor. As of December 31, 2024, there were 193 issues in the Underlying Index. The Underlying Index is reconstituted quarterly. The Fund generally reconstitutes its portfolio in accordance with the Underlying Index. </div> <div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” its Underlying Index and does not seek temporary defensive positions when markets decline or appear overvalued. </div> <div style="margin-top: 6pt;">NTI uses a representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div> <div style="margin-top: 6pt;">Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index and in American Depositary Receipts (“ADRs”) and Global Depositary Receipts (“GDRs”) (collectively “Depositary Receipts”) based on the securities in the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts, options on futures contracts and foreign currency contracts, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">The Underlying Index is created and sponsored by NTI, as the Index Provider. NTI also serves as the investment adviser to the Fund. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div> <div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received). </div> <div style="margin-top: 6pt;">From time to time the Fund may focus its investments (i.e., invest more than 15% of its total assets) in one or more particular countries or geographic regions. </div> <div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the financial sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the financial sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time. Principal Risks <div style="margin-top: 6pt;">Equity Securities Risk is the risk that the values of the equity securities owned by the Fund may be more volatile and underperform other asset classes and the general securities markets.</div> <div style="margin-top: 6pt;">Mid Cap Stock Risk is the risk that stocks of mid-sized companies may be subject to more abrupt or erratic market movements than stocks of larger, more established companies</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">, and may lack sufficient market liquidity. Mid-sized companies may have limited product lines or financial resources, and may be dependent upon a particular niche of the market, or may be dependent upon a small or inexperienced management group. Securities of smaller companies may trade less frequently and in lower volume than the securities of larger companies, which could lead to higher transaction costs. Generally the smaller the company size, the greater the risk.</div> <div style="margin-top: 6pt;">Foreign Securities Risk is the risk that investing in foreign (non-U.S.) securities may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies, due to less liquid markets and adverse economic, political, diplomatic, financial, and regulatory factors. Foreign governments may impose limitations on foreigners’ ownership of interests in local issuers, restrictions on the ability to repatriate assets, and may also impose taxes. Any of these events could cause the value of the Fund’s investments to decline. Foreign banks, agents and securities depositories that hold the Fund’s foreign assets may be subject to little or no regulatory oversight over, or independent evaluation, of their operations. Additional costs associated with investments in foreign securities may include higher custodial fees than those applicable to domestic custodial arrangements and transaction costs of foreign currency conversions. Unless the Fund has hedged its foreign currency exposure, foreign securities risk also involves the risk of negative foreign currency rate fluctuations, which may cause the value of securities denominated in such foreign currency (or other instruments through which the Fund has exposure to foreign currencies) to decline in value. Currency exchange rates may fluctuate significantly over short periods of time. Currency hedging strategies, if used, are not always successful. For instance, forward foreign currency exchange contracts, if used by the Fund, could reduce performance if there are unanticipated changes in currency exchange rates.</div> <div style="margin-top: 6pt;">Emerging Markets Risk is the risk that emerging markets are generally subject to greater market volatility, political, social and economic instability, uncertain trading markets and more governmental limitations on foreign investments than more developed markets. In addition, companies operating in emerging markets may be subject to lower trading volumes and greater price volatility than companies</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;"> in more developed markets. Emerging market economies may be based on only a few industries, may be highly vulnerable to changes in local and global trade conditions, and may suffer from extreme and volatile debt burdens or inflation rates. Companies in emerging market countries generally may be subject to less stringent regulatory, disclosure, financial reporting, accounting, auditing and recordkeeping standards than companies in more developed countries. As a result, information, including financial information, about such companies may be less available and reliable, which can impede the Fund’s ability to evaluate such companies. Securities law and the enforcement of systems of taxation in many emerging market countries may change quickly and unpredictably, and the ability to bring and enforce actions (including bankruptcy, confiscatory taxation, expropriation, nationalization of a company’s assets, restrictions on foreign ownership of local companies, restrictions on withdrawing assets from the country, protectionist measures and practices such as share blocking), or to obtain information needed to pursue or enforce such actions, may be limited. Investments in emerging market securities may be subject to additional transaction costs, delays in settlement procedures, unexpected market closures, and lack of timely information.</div> <div style="margin-top: 6pt;">Geographic Risk is the risk that if the Fund invests a significant portion of its total assets in certain issuers within the same country or geographic region, an adverse economic, business or political development affecting that country or region may affect the value of the Fund’s investments more, and the Fund’s investments may be more volatile, than if the Fund’s investments were not so concentrated in such country or region.</div> <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> •Financial Sector Risk is the risk that the financial sector can be significantly affected by changes in interest rates, government regulation, the rate of corporate and consumer debt defaulted, price competition, and the availability and cost of capital, among other factors. <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Dividend Risk is the risk that an issuer of stock held by the Fund may choose not to declare a dividend or the dividend rate might not remain at current levels. Dividend paying stocks might not experience the same level of earnings growth or capital appreciation as non-dividend paying stocks. The Fund’s performance during a broad market advance could suffer because dividend paying stocks may not experience the same capital appreciation as non-dividend paying stocks. </div> <div style="margin-top: 6pt;">Volatility Risk is the risk that the actual level of volatility experienced by the Fund may be greater or lower than the targeted overall volatility of the Underlying Index. Although the Underlying Index is designed to have a targeted overall volatility that is greater than that of the Parent Index, there is no guarantee that it will have the targeted overall volatility. The Fund will continue to seek to track the Underlying Index even if the Underlying Index does not have the targeted overall volatility. There is also the risk that the Fund may experience volatility greater or lower than that of the Underlying Index as a result of tracking error. A portfolio of securities with greater volatility is generally considered to have a higher risk profile than a portfolio with lower volatility.</div> <div style="margin-top: 6pt;">Quality Factor Risk is the risk that the past performance of companies that have exhibited quality characteristics does not continue or the returns on securities issued by such companies may be less than returns from other styles of investing or the overall stock market. There may be periods when quality investing is out of favor and during which time the Fund's performance may suffer.</div> <div style="margin-top: 6pt;">Depositary Receipts Risk Foreign securities may trade in the form of depositary receipts. In addition to investment risks associated with the underlying issuer, depositary receipts may expose the Fund to additional risks associated with non-uniform terms that apply to depositary receipt programs, including credit exposure to the depository bank and to the sponsors and other parties with whom the depository bank establishes the programs, currency, political, economic, market risks and the risks of an illiquid market for depositary receipts. Depositary receipts are generally subject to the same risks as the foreign securities that they evidence or into which they may be converted. Depositary receipts may not track the price of the underlying foreign securities on which they are based, may have limited voting </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">rights, and may have a distribution subject to a fee charged by the depository. As a result, equity shares of the underlying issuer may trade at a discount or premium to the market price of the depositary receipts.</div> <div style="margin-top: 6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase. </div> <div style="margin-top: 6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">its Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="margin-top: 6pt;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting. This risk may be heightened because of its investments in non-U.S. securities.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top: 6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div> •Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies.•Forward Foreign Currency Contracts Risk is the risk that, if forward prices increase, a loss will occur to the extent that the agreed upon purchase price of the currency exceeds the price of the currency that was agreed to be sold. <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> <div style="margin-top: 6pt;">Valuation Risk is the risk that the sale price the Fund could receive for a portfolio security may differ from the Fund’s valuation of the security, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. In addition, the value of the securities in the Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;"> indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the period shown in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (12/31/2020): 22.83% </div> <div style="margin-top: 6pt;">Worst Quarter (3/31/2020): -26.51%</div> Best Quarter 2020-12-31 0.2283 Worst Quarter 2020-03-31 -0.2651 Average Annual Total Returns(for the periods ended December 31, 2024) 0.0581 0.0615 0.0576 0.0415 0.0486 0.0465 0.0463 0.0467 0.0444 0.0553 0.0410 0.0480 0.0610 0.0661 0.0620 Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® iBoxx® 3-Year Target Duration TIPS Index Fund Investment Objective <div style="margin-top:6pt;">The Fund seeks to provide investment results that, before fees and expenses, correspond generally to the price and yield performance of the iBoxx 3-Year Target Duration TIPS Index (the “Underlying Index”).</div> Fees and Expenses of the Fund <div style="margin-top:6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0018 0.0000 0.0001 0.0019 -0.0001 0.0018 March 1, 2026 Example <div style="margin-top:6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The </div><div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 18 60 106 242 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 71% of the average value of its portfolio. 0.71 Principal Investment Strategies <div style="margin-top:6pt;">The Underlying Index is designed to reflect the performance of a selection of inflation protected public obligations of the U.S. Treasury, commonly known as “TIPS,” with a targeted average modified adjusted duration, as defined by S&P Dow Jones Indices LLC as the Index Provider (“Index Provider” or “SPDJI”), of approximately three years. The Underlying Index includes publicly issued TIPS that have maturity dates of at least one year but not more than ten years from an index rebalancing date. TIPS are securities issued by the U.S. Treasury that are designed to provide inflation protection to investors. TIPS’ principal and interest payments are linked to an official inflation measure (as measured by the Consumer Price Index for All Urban Consumers, or CPI-U) and the payments are supported by the full faith and credit of the United States. As of December 31, 2024, there were 26 TIPS in the Underlying Index. The components of the Underlying Index are weighted by the Index Provider to achieve the targeted average modified adjusted duration and its composition is rebalanced monthly. The Fund generally rebalances its portfolio in accordance with the Underlying Index. </div><div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. NTI generally intends to replicate the constituent securities of the Fund’s Underlying Index. “Replication” is an indexing strategy in which a fund invests in substantially all of the securities in its underlying index in approximately the same proportions as in the underlying index. NTI may use a “representative sampling” strategy in certain circumstances, such as when it may not be possible or practicable to fully implement a replication strategy. Representative sampling is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. When the Fund uses representative sampling, it may or may not hold all of the securities that are included in the Underlying Index. </div><div style="margin-top:6pt;">Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts and options on futures contracts, to-be-announced (“TBA”) transactions, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div><div style="margin-top:6pt;">The Underlying Index is sponsored by the Index Provider, an organization that is independent of the Fund and NTI. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div><div style="margin-top:6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received). </div><div style="margin-top:6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. For purposes of this limitation, securities of the U.S. government (including its agencies and instrumentalities) are not considered to be issued by members of any industry.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. For purposes of this limitation, securities of the U.S. government (including its agencies and instrumentalities) are not considered to be issued by members of any industry. Principal Risks <div style="margin-top:6pt;">Inflation Protected Security Risk is the risk that the value of inflation protected securities, such as TIPS, generally will fluctuate in response to changes in real interest rates, generally decreasing when real interest rates rise and increasing when real interest rates fall. In addition, interest payments on inflation-protected securities will generally vary up or down along with the rate of inflation. Real interest rates are generally measured as a nominal interest less an inflation rate. As such, investors should be aware that an investment in TIPS over a particular timeframe may decrease in value even in an inflationary environment. There can be no assurance that the inflation index used will accurately measure the real rate of inflation in the prices of goods and services. Because of their inflation adjustment feature, inflation-protected bonds typically have lower yields than conventional fixed-rate bonds. In addition, the market for inflation-indexed securities may be less developed or liquid, and more volatile, than certain other securities markets. In addition, positive adjustments to principal generally will result in taxable income to the Fund at the time of such adjustments (which generally would be distributed by the Fund as part of its taxable dividends), even though the principal amount is not paid until maturity.</div> <div style="margin-top:6pt;">Income Risk is the risk that the Fund's income may decline due to a decline in inflation (or deflation) or due to changes in inflation expectations.</div> <div style="margin-top:6pt;">Interest Rate/Maturity Risk is the risk that the value of the Fund’s fixed-income assets will decline because of rising interest rates. In general, securities with longer maturities or durations are more sensitive to interest rate changes. Changing interest rates, including rates that fall below zero, </div><div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">may have unpredictable effects on the markets and the Fund’s investments, may result in heightened market volatility, may impact the liquidity of fixed-income securities and of the Fund, and may detract from Fund performance. A low or negative interest rate environment could cause the Fund’s earnings to fall below the Fund’s expense ratio, resulting in a negative yield and a decline in the Fund’s share price. An increase in interest rates may cause investors to move out of fixed incomes securities on a large scale, which could adversely affect the price of fixed income securities, lead to heightened volatility in the fixed-income markets and may adversely affect the liquidity of certain fixed-income investments.</div> <div style="margin-top:6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase.</div> <div style="margin-top:6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="margin-top:6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting.</div> <div style="margin-top:6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> <div style="margin-top:6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div><div style="margin-top:6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top:6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div>•Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies. <div style="margin-top:6pt;">TBA Transactions Risk is the risk of loss if the securities received are less favorable than what was anticipated by the Fund when entering into the TBA transaction. TBA transactions also involve the risk that the counterparty will fail to deliver the securities, exposing the Fund to further losses. Default or bankruptcy of a counterparty to a TBA transaction would expose the Fund to possible losses because of adverse market action, expenses or delays in connection with the purchase or sale of the pools of mortgage pass-through securities specified in the TBA transaction. Whether or not the Fund takes delivery of the securities at the termination date of a TBA transaction, the Fund will nonetheless be exposed to changes in the value of the underlying investments during the term of the agreement.</div> <div style="margin-top:6pt;">Credit (or Default) Risk is the risk that the inability or unwillingness of an issuer or guarantor of a fixed-income security, or a counterparty to a TBA, repurchase or other transaction, to meet its payment or other financial obligations will adversely affect the value of the Fund’s investments and its returns. The credit quality of a debt security or of the issuer of a debt security held by the Fund could deteriorate rapidly, which may impair the Fund’s liquidity or cause a deterioration in the Fund’s NAV. The Fund could also be delayed or hindered in its enforcement of rights against an issuer, guarantor or counterparty. The degree of credit risk depends on the issuer’s or counterparty’s financial condition and on the terms of the securities.</div> <div style="margin-top:6pt;">Prepayment (or Call) Risk is the risk that an issuer could exercise its right to pay principal on callable debt securities held by the Fund earlier than expected. Issuers may be more likely to prepay when interest rates fall, when credit spreads change, or when an issuer’s credit quality improves. If this happens, the Fund will not benefit from the rise in the market price of the securities that normally accompanies a decline in interest rates, and will be forced to reinvest prepayment proceeds in lower yielding securities, which may reduce the Fund’s returns. The Fund may also lose any premium it paid to purchase the securities.</div> <div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top:6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year and (B) how the Fund’s average annual returns compare with those of a broad measure of market performance. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year and (B) how the Fund’s average annual returns compare with those of a broad measure of market performance. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top:6pt;">For the periods shown in the bar chart above: </div><div style="margin-top:6pt;">Best Quarter (6/30/2020): 3.31% </div><div style="margin-top:6pt;">Worst Quarter (9/30/2022): -3.28% </div> Best Quarter 2020-06-30 0.0331 Worst Quarter 2022-09-30 -0.0328 Average Annual Total Returns(for the periods ended December 31, 2024) 0.0396 0.0318 0.0248 0.0227 0.0151 0.0135 0.0232 0.0173 0.0142 0.0125 -0.0033 0.0135 0.0415 0.0337 0.0263 In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the iBoxx 3-Year Target Duration TIPS Index to the Bloomberg U.S. Aggregate Bond Index. The Fund will continue to compare its performance to the iBoxx 3-Year Target Duration TIPS Index, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. <div style="margin-top:6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® iBoxx® 5-Year Target Duration TIPS Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks to provide investment results that, before fees and expenses, correspond generally to the price and yield performance of the iBoxx 5-Year Target Duration TIPS Index (the “Underlying Index”).</div> Fees and Expenses of the Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0018 0.0000 0.0001 0.0019 -0.0001 0.0018 March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 18 60 106 242 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 42% of the average value of its portfolio. 0.42 Principal Investment Strategies <div style="margin-top: 6pt;">The Underlying Index is designed to reflect the performance of a selection of inflation protected public obligations of the U.S. Treasury, commonly known as “TIPS,” with a targeted average modified adjusted duration, as defined by S&P Dow Jones Indices LLC as the Index Provider (“Index Provider” or “SPDJI”), of approximately five years. The Underlying Index includes publicly issued TIPS that have maturity dates of at least three years but not more than twenty years from an index rebalancing date. TIPS are securities issued by the U.S. Treasury that are designed to provide inflation protection to investors. TIPS’ principal and interest payments are linked to an official inflation measure (as measured by the Consumer Price Index for All Urban Consumers, or CPI-U) and the payments are supported by the full faith and credit of the United States. As of December 31, 2024, there were 24 TIPS in the Underlying Index. The components of the Underlying Index are weighted by the Index Provider to achieve the targeted average modified adjusted duration and its composition is rebalanced monthly. The Fund generally rebalances its portfolio in accordance with the Underlying Index. </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. NTI generally intends to replicate the constituent securities of the Fund’s Underlying Index. “Replication” is an indexing strategy in which a fund invests in substantially all of the securities in its underlying index in approximately the same proportions as in the underlying index. NTI may use a “representative sampling” strategy in certain circumstances, such as when it may not be possible or practicable to fully implement a replication strategy. Representative sampling is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. When the Fund uses representative sampling, it may or may not hold all of the securities that are included in the Underlying Index. </div> <div style="margin-top: 6pt;">Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts and options on futures contracts, to-be-announced (“TBA”) transactions, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div> <div style="margin-top: 6pt;">The Underlying Index is sponsored by the Index Provider, an organization that is independent of the Fund and NTI. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div> <div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received). </div> <div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. For purposes of this limitation, securities of the U.S. government (including its agencies and instrumentalities) are not considered to be issued by members of any industry.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. For purposes of this limitation, securities of the U.S. government (including its agencies and instrumentalities) are not considered to be issued by members of any industry. Principal Risks <div style="margin-top: 6pt;">Inflation Protected Security Risk is the risk that the value of inflation protected securities, such as TIPS, generally will fluctuate in response to changes in real interest rates, generally decreasing when real interest rates rise and increasing when real interest rates fall. In addition, interest payments on inflation-protected securities will generally vary up or down along with the rate of inflation. Real interest rates are generally measured as a nominal interest less an inflation rate. As such, investors should be aware that an investment in TIPS over a particular timeframe may decrease in value even in an inflationary environment. There can be no assurance that the inflation index used will accurately measure the real rate of inflation in the prices of goods and services. Because of their inflation adjustment feature, inflation-protected bonds typically have lower yields than conventional fixed-rate bonds. In addition, the market for inflation-indexed securities may be less developed or liquid, and more volatile, than certain other securities markets. In addition, positive adjustments to principal generally will result in taxable income to the Fund at the time of such adjustments (which generally would be distributed by the Fund as part of its taxable dividends), even though the principal amount is not paid until maturity.</div> <div style="margin-top: 6pt;">Income Risk is the risk that the Fund's income may decline due to a decline in inflation (or deflation) or due to changes in inflation expectations.</div> <div style="margin-top: 6pt;">Interest Rate/Maturity Risk is the risk that the value of the Fund’s fixed-income assets will decline because of rising interest rates. In general, securities with longer maturities or durations are more sensitive to interest rate changes. Changing interest rates, including rates that fall below zero, </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">may have unpredictable effects on the markets and the Fund’s investments, may result in heightened market volatility, may impact the liquidity of fixed-income securities and of the Fund, and may detract from Fund performance. A low or negative interest rate environment could cause the Fund’s earnings to fall below the Fund’s expense ratio, resulting in a negative yield and a decline in the Fund’s share price. An increase in interest rates may cause investors to move out of fixed incomes securities on a large scale, which could adversely affect the price of fixed income securities, lead to heightened volatility in the fixed-income markets and may adversely affect the liquidity of certain fixed-income investments.</div> <div style="margin-top: 6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failure, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase.</div> <div style="margin-top: 6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting.</div> <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top: 6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div>•Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation <div style="line-height: 12.10pt; margin-left: 14.97pt; margin-top: 0.00pt; text-align: left;">between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies.</div> <div style="margin-top: 6pt;">TBA Transactions Risk is the risk of loss if the securities received are less favorable than what was anticipated by the Fund when entering into the TBA transaction. TBA transactions also involve the risk that the counterparty will fail to deliver the securities, exposing the Fund to further losses. Default or bankruptcy of a counterparty to a TBA transaction would expose the Fund to possible losses because of adverse market action, expenses or delays in connection with the purchase or sale of the pools of mortgage pass-through securities specified in the TBA transaction. Whether or not the Fund takes delivery of the securities at the termination date of a TBA transaction, the Fund will nonetheless be exposed to changes in the value of the underlying investments during the term of the agreement.</div> <div style="margin-top: 6pt;">Credit (or Default) Risk is the risk that the inability or unwillingness of an issuer or guarantor of a fixed-income security, or a counterparty to a TBA, repurchase or other transaction, to meet its payment or other financial obligations will adversely affect the value of the Fund’s investments and its returns. The credit quality of a debt security or of the issuer of a debt security held by the Fund could deteriorate rapidly, which may impair the Fund’s liquidity or cause a deterioration in the Fund’s NAV. The Fund could also be delayed or hindered in its enforcement of rights against an issuer, guarantor or counterparty. The degree of credit risk depends on the issuer’s or counterparty’s financial condition and on the terms of the securities.</div> <div style="margin-top: 6pt;">Prepayment (or Call) Risk is the risk that an issuer could exercise its right to pay principal on callable debt securities held by the Fund earlier than expected. Issuers may be more likely to prepay when interest rates fall, when credit spreads change, or when an issuer’s credit quality improves. If this happens, the Fund will not benefit from the rise in the market price of the securities that normally accompanies a decline in interest rates, and will be forced to reinvest prepayment proceeds in lower yielding securities, which may reduce the Fund’s returns. The Fund may also lose any premium it paid to purchase the securities.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year and (B) how the Fund’s average annual returns compare with those of a broad measure of market performance. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year and (B) how the Fund’s average annual returns compare with those of a broad measure of market performance. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the periods shown in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (12/31/2023): 4.53% </div> <div style="margin-top: 6pt;">Worst Quarter (6/30/2022): -4.68% </div> Best Quarter 2023-12-31 0.0453 Worst Quarter 2022-06-30 -0.0468 Average Annual Total Returns (for the periods ended December 31, 2024) 0.0219 0.0226 0.0242 0.0055 0.0056 0.0122 0.0128 0.0102 0.0135 0.0125 -0.0033 0.0135 0.0245 0.0248 0.0256 In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the iBoxx 5-Year Target Duration TIPS Index to the Bloomberg U.S. Aggregate Bond Index. The Fund will continue to compare its performance to the iBoxx 5-Year Target Duration TIPS Index, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® Disciplined Duration MBS Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of The ICE BofA® Constrained Duration US Mortgage Backed Securities IndexSM (the “Underlying Index”).</div> Fees and Expenses of the Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0020 0.0000 0.0001 0.0021 -0.0001 0.0020 March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">then sell all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 20 67 117 267 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 31% of the average value of its portfolio. 0.31 Principal Investment Strategies <div style="margin-top: 6pt;">The Underlying Index is designed to reflect the performance of a selection of investment-grade US agency residential mortgage backed pass-through securities. The term “US agency mortgage-backed pass-through security” (“MBS”) refers to a category of pass-through securities backed by pools of mortgages and issued by one of the following US government agencies: the Federal National Mortgage Association (FNMA or Fannie Mae), the Federal Home Loan Mortgage Corporation (FHLMC or Freddie Mac) or the Government National Mortgage Association (GNMA or Ginnie Mae) (each a “US Agency”). The Underlying Index is formed by grouping the universe of individual fixed-rate MBS pools into generic cohorts according to the following parameters: (i) agency; (ii) mortgage program; (iii) pass-through coupon; and (iv) origination year. These generic cohorts are then assessed based on certain criteria, as determined by ICE Data Indices, LLC as the Index Provider (“Index Provider” or “ICE”), to determine eligibility for inclusion in the Underlying Index. The constituent securities of the Underlying Index are MBS pools </div><div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">that meet the parameters of generic cohorts included in the Underlying Index. MBS that are eligible for inclusion in the Underlying Index must (a) be publicly issued by a US Agency, (b) have a weighted average remaining time to final stated maturity of at least one year, (c) have at least $5 billion or more of outstanding face value in the coupon for a given agency program, (d) have at least $1 billion or more of outstanding face value at the time of inclusion in the Underlying Index and at least $250 million to remain in the Underlying Index and (e) are characterized by one or more of the following fixed-rate mortgage programs: 30-year, 20-year, and 15-year maturities. The Underlying Index constituents are capitalization-weighted, based on their outstanding face value times price plus accrued interest, adjusted by the Index Provider, to achieve an effective duration that is generally between 3.25 and 4.25 years. Balloon, mobile home, graduated payment and quarter coupon fixed rate mortgages are excluded from the Underlying Index, as are all collateralized mortgage obligations. </div><div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. </div><div style="margin-top: 6pt;">NTI uses a representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div><div style="margin-top: 6pt;">The Fund generally will invest under normal circumstances at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index and in “TBA Transactions” (defined below) that represent securities in the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts and options on futures contracts, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. Most transactions in mortgage pass-through securities occur through standardized</div><div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;"> contracts for future delivery in which the exact mortgage pools to be delivered are not specified until a few days prior to settlement, referred to as a “to-be announced transaction” or “TBA Transaction.” In a TBA Transaction, the buyer and seller agree upon general trade parameters such as agency, coupon rate, settlement date, par amount and price. The actual pools delivered generally are determined two days prior to the settlement date. The Fund expects to enter into such contracts on a regular basis, and pending settlement of such contracts, the Fund will invest its assets in liquid, short-term instruments, which may include shares of money market funds advised by NTI or its affiliates. The Fund will assume its pro rata share of the fees and expenses of any money market fund, in which it may invest, in addition to the Fund’s own fees and expenses. </div><div style="margin-top: 6pt;">The Underlying Index is sponsored by the Index Provider. The Index Provider is not affiliated with the Fund or NTI. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index in accordance with a published methodology and disseminates information regarding the market value of the Underlying Index. The Underlying Index is rebalanced on the last calendar day of each month. The Fund generally rebalances its portfolio in accordance with the Underlying Index. As of December 31, 2024, there were 136 MBS in the Underlying Index. </div><div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received).</div><div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. For purposes of this limitation, securities of the U.S. government (including its agencies and instrumentalities) are not considered to be issued by members of any industry.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. For purposes of this limitation, securities of the U.S. government (including its agencies and instrumentalities) are not considered to be issued by members of any industry. Principal Risks <div style="margin-top: 6pt;">Mortgage-Backed Pass-Through Securities Risk is the risk of investing in mortgage-backed securities issued by a US Agency. Mortgage-backed securities may be less liquid than other bonds, and may be more sensitive than other bonds to the market’s perception of issuers and creditworthiness of payees, particularly in declining general economic conditions when concern regarding mortgagees’ ability to pay (e.g., the ability of homeowners, commercial mortgagees, consumers with student loans, automobile loans or credit card debtholders to make payments on the underlying loan pools) rises, which may result in the Fund experiencing difficulty selling or valuing these securities. In addition, these securities may not be backed by the full faith and credit of the U.S. government, have experienced extraordinary weakness and volatility at various times in recent years, and may decline quickly in the event of a substantial economic or market downturn. Mortgage-backed securities are subject to Credit (or Default) Risk, Interest Rate/Maturity Risk, Debt Extension Risk and Prepayment (or Call) Risk. Because of these risks, mortgage-backed securities react differently to changes in interest rates than other bonds. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain mortgage-backed securities. While agency mortgage-backed securities are guaranteed as to the timely payment of interest and principal by a government entity, they are not guaranteed as to market price, which will fluctuate.</div> <div style="margin-top: 6pt;">U.S. Government Securities Risk is the risk that the U.S. government will not provide financial support to its agencies, instrumentalities or sponsored enterprises if it is not obligated to do so by law. Many U.S. government securities that may be purchased by the Fund are not backed by the full faith and credit of the United States. The maximum potential liability of the issuers of some U.S. government securities may greatly exceed their current resources, including any legal right to support from the U.S. Treasury. It is possible that the issuers of such securities will not have the funds to meet their payment obligations in the future.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Income Risk is the risk that the Fund’s income may decline when interest rates fall. This decline can occur because the Fund must invest in lower-yielding bonds as bonds in its portfolio mature, bonds in the Underlying Index are substituted or the Fund otherwise needs to purchase additional bonds.</div> <div style="margin-top: 6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase. </div> <div style="margin-top: 6pt;">Cash Transactions Risk is the risk from the Fund effecting creation and redemption orders of its shares entirely for cash, rather than for in-kind securities. The Fund may have to sell portfolio securities at inopportune times in order to obtain the cash needed to meet redemption orders. This may cause the Fund to sell a security or other financial instrument and recognize a capital gain or loss that might not have been incurred if it had not effected a redemption order entirely for cash. As such, investments in Fund shares may be less tax-efficient than an investment in an ETF that meets redemption orders entirely in-kind with portfolio securities. The use of all cash creation and redemption orders may also cause the Fund’s shares to trade in the secondary market at wider bid-ask spreads and/or greater premiums or discounts to the Fund’s NAV. To the extent that the maximum additional variable charge for cash creation or cash redemption transactions is insufficient to cover the transaction costs of purchasing or selling portfolio securities, the Fund’s performance could be negatively impacted.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="margin-top: 6pt;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemp</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">tion transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> <div style="margin-top: 6pt;">Credit (or Default) Risk is the risk that the inability or unwillingness of an issuer or guarantor of a fixed-income security, or a counterparty to a TBA, repurchase or other transaction, to meet its payment or other financial obliga</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">tions will adversely affect the value of the Fund’s investments and its returns. The credit quality of a debt security or of the issuer of a debt security held by the Fund could deteriorate rapidly, which may impair the Fund’s liquidity or cause a deterioration in the Fund’s NAV. The Fund could also be delayed or hindered in its enforcement of rights against an issuer, guarantor or counterparty. The degree of credit risk depends on the issuer’s or counterparty’s financial condition and on the terms of the securities. </div> <div style="margin-top: 6pt;">Debt Extension Risk is the risk that when interest rates rise an issuer will exercise its right to pay principal on certain debt securities held by the Fund later than expected. This will cause the value of the security, and the Fund’s NAV, to decrease, and the Fund may lose opportunities to invest in higher yielding securities.</div> <div style="margin-top: 6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div> •Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation <div style="line-height: 12.10pt; margin-left: 14.97pt; margin-top: 0.00pt; text-align: left;">between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies.</div> <div style="margin-top: 6pt;">High Portfolio Turnover Risk is the risk that active and frequent trading of the Fund’s portfolio securities may result in increased transaction costs to the Fund, including brokerage commissions, dealer mark-ups and other transaction costs, which could reduce the Fund’s return.</div> <div style="margin-top: 6pt;">Interest Rate/Maturity Risk is the risk that the value of the Fund’s fixed-income assets will decline because of rising interest rates. In general, securities with longer maturities or durations are more sensitive to interest rate changes. Changing interest rates, including rates that fall below zero, may have unpredictable effects on the markets and the Fund’s investments, may result in heightened market volatility, may impact the liquidity of fixed-income securities and of the Fund, and may detract from Fund performance. A low or negative interest rate environment could cause the Fund’s earnings to fall below the Fund’s expense ratio, resulting in a negative yield and a decline in the Fund’s share price. An increase in interest rates may cause investors to move out of fixed incomes securities on a large scale, which could adversely affect the price of fixed income securities, lead to heightened volatility in the fixed-income markets and may adversely affect the liquidity of certain fixed-income investments. The average effective duration of the Fund’s portfolio securities may be longer or shorter than the average effective duration of the MBS of the Underlying Index. Although the Underlying Index is designed so that the average effective duration of the MBS represented in the Index generally will range between 3.25 and 4.25 years, there is no guarantee that it will do so. The Fund will continue to seek to track the Underlying Index. There is also the risk that the Fund may have a longer or shorter average effective duration than that of the MBS in the Underlying Index as a result of tracking error. A portfolio of securities with a longer average effective duration is generally considered to have a higher risk profile than a portfolio with a shorter average effective duration.</div> <div style="margin-top: 6pt;">Liquidity Risk is the risk that certain portfolio securities may be less liquid than others, which may make them difficult or impossible to sell at the time and the price that the </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Fund would like, adversely affecting the value of the Fund’s investments and its returns. Illiquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. Liquidity risk may result from the lack of an active market, reduced number and capacity of traditional market participants to make a market in fixed income securities, and may be magnified in a rising interest rate environment or other circumstances where investor redemptions from fixed income funds may be higher than normal, causing increased supply in the market due to selling activity. The market for certain investments may become illiquid under adverse market or economic conditions independent of any specific adverse changes in the conditions of a particular issuer. In such cases, the Fund, due to limitations on investments in illiquid securities and/or purchasing and selling such investments, may be unable to achieve a high degree of correlation with the Underlying Index. Additionally, in adverse market conditions, the Fund’s market price may begin to reflect illiquidity or pricing uncertainty of the Fund’s portfolio securities. This could lead to the Fund’s shares trading at a price that is higher or lower than the Fund’s NAV. At times, such differences may be significant.</div> <div style="margin-top: 6pt;">Prepayment (or Call) Risk is the risk that an issuer could exercise its right to pay principal on callable debt securities held by the Fund earlier than expected. Issuers may be more likely to prepay when interest rates fall, when credit spreads change, or when an issuer’s credit quality improves. If this happens, the Fund will not benefit from the rise in the market price of the securities that normally accompanies a decline in interest rates, and will be forced to reinvest prepayment proceeds in lower yielding securities, which may reduce the Fund’s returns. The Fund may also lose any premium it paid to purchase the securities.</div> <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> <div style="margin-top: 6pt;">TBA Transactions Risk is the risk of loss if the securities received are less favorable than what was anticipated by the Fund when entering into the TBA transaction. TBA trans</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">actions also involve the risk that the counterparty will fail to deliver the securities, exposing the Fund to further losses. Default or bankruptcy of a counterparty to a TBA transaction would expose the Fund to possible losses because of adverse market action, expenses or delays in connection with the purchase or sale of the pools of mortgage pass-through securities specified in the TBA transaction. Whether or not the Fund takes delivery of the securities at the termination date of a TBA transaction, the Fund will nonetheless be exposed to changes in the value of the underlying investments during the term of the agreement.</div> <div style="margin-top: 6pt;">Valuation Risk is the risk that the sale price the Fund could receive for a portfolio security may differ from the Fund’s valuation of the security, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. In addition, the value of the securities in the Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year and (B) how the Fund’s average annual returns compare with those of a broad measure of market performance. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year and (B) how the Fund’s average annual returns compare with those of a broad measure of market performance. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the period shown in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (12/31/2023): 5.35% </div> <div style="margin-top: 6pt;">Worst Quarter (3/31/2022): -4.53%</div> Best Quarter 2023-12-31 0.0535 Worst Quarter 2022-03-31 -0.0453 Average Annual Total Returns (for the periods ended December 31, 2024) 0.0222 0.0010 0.0102 0.0063 -0.0115 -0.0030 0.0131 -0.0044 0.0021 0.0125 -0.0033 0.0135 0.0279 0.0064 0.0151 In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the ICE BofA® Constrained Duration US Mortgage Backed Securities IndexSM to the Bloomberg U.S. Aggregate Bond Index. The Fund will continue to compare its performance to the ICE BofA® Constrained Duration US Mortgage Backed Securities IndexSM, which reflects the market segments in which the Fund invests. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® Credit-Scored US Corporate Bond Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Northern Trust US Corporate Bond Quality Value IndexSM (the “Underlying Index”).</div> Fees and Expenses of the Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0015 0.0000 0.0001 0.0016 -0.0001 0.0015 March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 15 51 89 204 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 81% of the average value of its portfolio. 0.81 Principal Investment Strategies <div style="margin-top: 6pt;">The Underlying Index is designed to reflect the performance of a diversified universe of intermediate maturity, US-dollar denominated bonds of companies with investment grade credit quality, favorable valuations, and enhanced short-term and long-term solvency. Securities eligible for inclusion in the Underlying Index must meet the following criteria at each reconstitution of the Underlying Index: (a) they are issued in U.S. dollars; (b) they are publicly issued in the U.S. and registered with the SEC or eligible for resale under Rule 144A under the Securities Act of 1933; (c) they fall within a specified list of eligible security types; (d) they are either senior or subordinated debts; (e) they have a minimum credit rating of Baa3 or BBB-; (f) they have a final maturity of at least one year and up to (but not including) 10 years; and (g) they have $250 million or more in outstanding principal. </div> <div style="margin-top: 6pt;">Once all eligible securities have been identified, the Underlying Index then follows a rules-based methodology to select and weight securities, subject to certain constraints as described below, to optimize the Underlying Index’s exposure to a combined proprietary value score and a proprietary quality score, as determined by NTI acting in its capacity as index provider (“Index Provider”). Each of the value score and the quality score are based on various metrics obtained from company filings and recent price activity. The value score has multiple components, including: (a) valuation (e.g., to assess the relative value of the security versus other similar securities); (b) spread analysis (e.g., to assess the risk/return trade-off associated with each security versus other similar securities); and (c) solvency (e.g., to assess the corporation’s short term and long term solvency and also its risk of default). The quality score has three components: (i) management efficiency (e.g., corpo</div> <div style="line-height: 11.30pt; margin-top: 0.00pt; text-align: left;">rate finance activities); (ii) profitability (e.g., reliability and sustainability of financial performance); and (iii) solvency. The primary objective of the optimization process is to maximize exposure to securities with the highest value and quality scores and to maintain a similar effective duration profile relative to the Underlying Index's eligible universe. In addition, the optimization process also includes security level, sector, issuer level, low value and quality, duration band, and turnover constraints to seek to manage systematic risk. </div> <div style="margin-top: 6pt;">As of December 31, 2024, there were 2409 issues in the Underlying Index. The Underlying Index is reconstituted monthly. The Fund generally reconstitutes its portfolio in accordance with the Underlying Index. </div> <div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. </div> <div style="margin-top: 6pt;">NTI uses representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div> <div style="margin-top: 6pt;">The Fund generally will invest under normal circumstances at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of its Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts and options on futures, to-be-announced (“TBA”) transactions, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div> <div style="margin-top: 6pt;">The Underlying Index is created and sponsored by NTI, as the Index Provider. NTI also serves as the investment adviser to the Fund. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div> <div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received).</div> <div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approxi</div> <div style="line-height: 11.30pt; margin-top: 0.00pt; text-align: left;">mately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the financial sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approxi mately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the financial sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time. Principal Risks <div style="margin-top: 6pt;">Corporate Bond Risk. Corporate debt securities are subject to the risk of the issuer’s inability to meet principal and interest payments on the obligation and may also be subject to price volatility due to such factors as interest rate sensitivity, market perception of the creditworthiness of the issuer and general market liquidity. When interest rates rise, the value of corporate debt can be expected to decline. Debt securities with longer maturities tend to be more sensitive to interest rate movements than those with shorter maturities.</div> <div style="margin-top: 6pt;">Quality-Value Score Risk is the risk that the Fund’s investment in companies whose securities are believed to be undervalued will not appreciate in value as anticipated or the past performance of companies that have exhibited quality characteristics does not continue. Although the Underlying Index is designed to measure the performance of a portfolio of bonds with certain characteristics, there is no assurance that the Underlying Index or Fund will be comprised of such securities or that the Underlying Index's optimization process will achieve the intended results.</div> <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div>•Financial Sector Risk is the risk that the financial sector can be significantly affected by changes in interest rates, government regulation, the rate of corporate and consumer debt defaulted, price competition, and the availability and cost of capital, among other factors. <div style="line-height: 11.30pt; margin-top: 0.00pt; text-align: left;">Income Risk is the risk that the Fund’s income may decline when interest rates fall. This decline can occur because the Fund must invest in lower-yielding bonds as bonds in its portfolio mature, bonds in the Underlying Index are substituted or the Fund otherwise needs to purchase additional bonds.</div> <div style="margin-top: 6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase.</div> <div style="margin-top: 6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="line-height: 11.30pt; margin-top: 0.00pt; text-align: left;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top: 6pt;">Credit (or Default) Risk is the risk that the inability or unwillingness of an issuer or guarantor of a fixed-income security, or a counterparty to a TBA, repurchase or other </div> <div style="line-height: 11.30pt; margin-top: 0.00pt; text-align: left;">transaction, to meet its payment or other financial obligations will adversely affect the value of the Fund’s investments and its returns. The credit quality of a debt security or of the issuer of a debt security held by the Fund could deteriorate rapidly, which may impair the Fund’s liquidity or cause a deterioration in the Fund’s NAV. The Fund could also be delayed or hindered in its enforcement of rights against an issuer, guarantor or counterparty. The degree of credit risk depends on the issuer’s or counterparty’s financial condition and on the terms of the securities.</div> <div style="margin-top: 6pt;">Debt Extension Risk is the risk that when interest rates rise an issuer will exercise its right to pay principal on certain debt securities held by the Fund later than expected. This will cause the value of the security, and the Fund’s NAV, to decrease, and the Fund may lose opportunities to invest in higher yielding securities.</div> <div style="margin-top: 6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div>•Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the <div style="line-height: 10.90pt; margin-left: 14.97pt; margin-top: 0.00pt; text-align: left;">number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies.</div> <div style="margin-top: 6pt;">Interest Rate/Maturity Risk is the risk that the value of the Fund’s fixed-income assets will decline because of rising interest rates. In general, securities with longer maturities or durations are more sensitive to interest rate changes. Changing interest rates, including rates that fall below zero, may have unpredictable effects on the markets and the Fund’s investments, may result in heightened market volatility, may impact the liquidity of fixed-income securities and of the Fund, and may detract from Fund performance. A low or negative interest rate environment could cause the Fund’s earnings to fall below the Fund’s expense ratio, resulting in a negative yield and a decline in the Fund’s share price. An increase in interest rates may cause investors to move out of fixed incomes securities on a large scale, which could adversely affect the price of fixed income securities, lead to heightened volatility in the fixed-income markets and may adversely affect the liquidity of certain fixed-income investments.</div> <div style="margin-top: 6pt;">Liquidity Risk is the risk that certain portfolio securities may be less liquid than others, which may make them difficult or impossible to sell at the time and the price that the Fund would like, adversely affecting the value of the Fund’s investments and its returns. Illiquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. Liquidity Risk may result from the lack of an active market, reduced number and capacity of traditional market participants to make a market in fixed income securities, and may be magnified in a rising interest rate environment or other circumstances where investor redemptions from fixed income funds may be higher than normal, causing increased supply in the market due to selling activity. The market for certain investments may become illiquid under adverse market or economic conditions independent of any specific adverse changes in the conditions of a particular issuer. In such cases, the Fund, due to limitations on investments in illiquid securities and/or purchasing and selling such investments, may be unable to achieve a high degree of correlation with the Underlying Index. Additionally, in adverse market conditions, the Fund’s market price may begin to reflect illiquidity or pricing uncertainty of the Fund’s portfolio securities. This could lead to the Fund’s shares trading at a price that is higher or lower than the Fund’s NAV. At times, such differences may be significant.</div> <div style="margin-top: 6pt;">Rule 144A Securities Risk is the risk that limitations on the resale of Rule 144A securities may have an adverse effect on their marketability and may prevent the Fund from dispos</div> <div style="line-height: 11.30pt; margin-top: 0.00pt; text-align: left;">ing of them promptly at reasonable prices. There can be no assurance that an active trading market will exist at any time for such securities. Transaction costs may be higher for Rule 144A securities, and such securities may be difficult to value and may have significant volatility.</div> <div style="margin-top: 6pt;">Foreign Securities Risk is the risk that investing in foreign (non-U.S.) securities may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies, due to less liquid markets and adverse economic, political, diplomatic, financial, and regulatory factors. Foreign governments may impose limitations on foreigners’ ownership of interests in local issuers, restrictions on the ability to repatriate assets, and may also impose taxes. Any of these events could cause the value of the Fund’s investments to decline. Foreign banks, agents and securities depositories that hold the Fund’s foreign assets may be subject to little or no regulatory oversight over, or independent evaluation, of their operations. Additional costs associated with investments in foreign securities may include higher custodial fees than those applicable to domestic custodial arrangements and transaction costs of foreign currency conversions. Unless the Fund has hedged its foreign currency exposure, foreign securities risk also involves the risk of negative foreign currency rate fluctuations, which may cause the value of securities denominated in such foreign currency (or other instruments through which the Fund has exposure to foreign currencies) to decline in value. Currency exchange rates may fluctuate significantly over short periods of time. Currency hedging strategies, if used, are not always successful. For instance, forward foreign currency exchange contracts, if used by the Fund, could reduce performance if there are unanticipated changes in currency exchange rates.</div> <div style="margin-top: 6pt;">Prepayment (or Call) Risk is the risk that an issuer could exercise its right to pay principal on callable debt securities held by the Fund earlier than expected. Issuers may be more likely to prepay when interest rates fall, when credit spreads change, or when an issuer’s credit quality improves. If this happens, the Fund will not benefit from the rise in the market price of the securities that normally accompanies a decline in interest rates, and will be forced to reinvest prepayment proceeds in lower yielding securities, which may reduce the Fund’s returns. The Fund may also lose any premium it paid to purchase the securities.</div> <div style="margin-top: 6pt;">TBA Transactions Risk is the risk of loss if the securities received are less favorable than what was anticipated by the Fund when entering into the TBA transaction. TBA transactions also involve the risk that the counterparty will fail to deliver the securities, exposing the Fund to further losses. Default or bankruptcy of a counterparty to a TBA </div> <div style="line-height: 11.30pt; margin-top: 0.00pt; text-align: left;">transaction would expose the Fund to possible losses because of adverse market action, expenses or delays in connection with the purchase or sale of the pools of mortgage pass-through securities specified in the TBA transaction. Whether or not the Fund takes delivery of the securities at the termination date of a TBA transaction, the Fund will nonetheless be exposed to changes in the value of the underlying investments during the term of the agreement.</div> <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> <div style="margin-top: 6pt;">Valuation Risk is the risk that the sale price the Fund could receive for a portfolio security may differ from the Fund’s valuation of the security, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. In addition, the value of the securities in the Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com. </div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the period shown in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (6/30/2020): 8.08% </div> <div style="margin-top: 6pt;">Worst Quarter (3/31/2022): -5.31% </div> Best Quarter 2020-06-30 0.0808 Worst Quarter 2022-03-31 -0.0531 Average Annual Total Returns (for the periods ended December 31, 2024) 0.0463 0.0167 0.0265 0.0257 0.0030 0.0137 0.0272 0.0072 0.0149 0.0125 -0.0033 0.0135 0.0422 0.0151 0.0261 0.0490 0.0219 0.0309 In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the Bloomberg U.S. Intermediate Corporate Bond Index to the Bloomberg U.S. Aggregate Bond Index. The Fund will continue to compare its performance to the Bloomberg U.S. Intermediate Corporate Bond Index, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may dif</div><div style="line-height: 11.30pt; margin-top: 0.00pt; text-align: left;">fer from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. </div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® Credit-Scored US Long Corporate Bond Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Northern Trust US Long Corporate Bond Quality Value IndexSM (the “Underlying Index”).</div> Fees and Expenses of the Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0015 0.0000 0.0001 0.0016 -0.0001 0.0015 March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses </div> <div style="line-height: 11.90pt; margin-top: 0.00pt; text-align: left;">remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 15 51 89 204 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 116% of the average value of its portfolio. 1.16 Principal Investment Strategies <div style="margin-top: 6pt;">The Underlying Index is designed to reflect the performance of a diversified universe of longer term maturity, US-dollar denominated bonds of companies with investment grade credit quality, favorable valuations, and enhanced short-term and long-term solvency. Securities eligible for inclusion in the Underlying Index must meet the following criteria at each reconstitution of the Underlying Index: (a) they are issued in U.S. dollars; (b) they are publicly issued in the U.S. and registered with the SEC or eligible for resale under Rule 144A under the Securities Act of 1933; (c) they fall within a specified list of eligible security types; (d) they are either senior or subordinated debts; (e) they have a minimum credit rating of Baa3 or BBB-; (f) they have a final maturity of 10 years or greater; and (g) they have $250 million or more in outstanding principal. </div> <div style="margin-top: 6pt;">Once all eligible securities have been identified, the Underlying Index then follows a rules-based methodology to select and weight securities, subject to certain constraints as described below, to optimize the Underlying Index’s exposure to a combined proprietary value score and a proprietary quality score, as determined by NTI acting in its capacity as index provider (“Index Provider”). Each of the value score and the quality score are based on various metrics obtained from company filings and recent price activity. The value score has multiple components, including: (a) valuation (e.g., to assess the relative value of the security versus other similar securities); (b) spread analysis </div> <div style="line-height: 11.90pt; margin-top: 0.00pt; text-align: left;">(e.g., to assess the risk/return trade-off associated with each security versus other similar securities); and (c) solvency (e.g., to assess the corporation’s short term and long term solvency and also its risk of default). The quality score has three components: (i) management efficiency (e.g., corporate finance activities); (ii) profitability (e.g., reliability and sustainability of financial performance); and (iii) solvency. The primary objective of the optimization process is to maximize exposure to securities with the highest value and quality scores and to maintain a similar effective duration profile relative to the Underlying Index’s eligible universe. In addition, the optimization process also includes security level, sector, issuer level, low value and quality, duration band, and turnover constraints to seek to manage systematic risk. </div> <div style="margin-top: 6pt;">As of December 31, 2024, there were 1432 issues in the Underlying Index. The Underlying Index is reconstituted monthly. The Fund generally reconstitutes its portfolio in accordance with the Underlying Index. </div> <div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. </div> <div style="margin-top: 6pt;">NTI uses representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div> <div style="margin-top: 6pt;">The Fund generally will invest under normal circumstances at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of its Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts and options on futures, to-be-announced (“TBA”) transactions, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div> <div style="margin-top: 6pt;">The Underlying Index is created and sponsored by NTI, as the Index Provider. NTI also serves as the investment adviser to the Fund. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div> <div style="line-height: 11.90pt; margin-top: 0.00pt; text-align: left;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received). </div> <div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. Principal Risks <div style="margin-top: 6pt;">Corporate Bond Risk is the risk the Fund faces because it invests primarily in bonds issued by corporations. Corporate debt securities are subject to the risk of the issuer’s inability to meet principal and interest payments on the obligation and may also be subject to price volatility due to such factors as interest rate sensitivity, market perception of the creditworthiness of the issuer and general market liquidity. When interest rates rise, the value of corporate debt can be expected to decline. Debt securities with longer maturities tend to be more sensitive to interest rate movements than those with shorter maturities.</div> <div style="margin-top: 6pt;">Quality-Value Score Risk is the risk that the Fund’s investment in companies whose securities are believed to be undervalued will not appreciate in value as anticipated or the past performance of companies that have exhibited quality characteristics does not continue. Although the Underlying Index is designed to measure the performance of a portfolio of bonds with certain characteristics, there is no assurance that the Underlying Index or Fund will be comprised of such securities or that the Underlying Index's optimization process will achieve the intended results.</div> <div style="margin-top: 6pt;">Income Risk is the risk that the Fund’s income may decline when interest rates fall. This decline can occur because the Fund must invest in lower-yielding bonds as bonds in its portfolio mature, bonds in the Underlying Index are substituted or the Fund otherwise needs to purchase additional bonds.</div> <div style="line-height: 11.90pt; margin-top: 0.00pt; text-align: left;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failure, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase.</div> <div style="margin-top: 6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="margin-top: 6pt;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities </div> <div style="line-height: 11.90pt; margin-top: 0.00pt; text-align: left;">selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top: 6pt;">Credit (or Default) Risk is the risk that the inability or unwillingness of an issuer or guarantor of a fixed-income security, or a counterparty to a TBA, repurchase or other </div> <div style="line-height: 11.90pt; margin-top: 0.00pt; text-align: left;">transaction, to meet its payment or other financial obligations will adversely affect the value of the Fund’s investments and its returns. The credit quality of a debt security or of the issuer of a debt security held by the Fund could deteriorate rapidly, which may impair the Fund’s liquidity or cause a deterioration in the Fund’s NAV. The Fund could also be delayed or hindered in its enforcement of rights against an issuer, guarantor or counterparty. The degree of credit risk depends on the issuer’s or counterparty’s financial condition and on the terms of the securities.</div> <div style="margin-top: 6pt;">Debt Extension Risk is the risk that when interest rates rise an issuer will exercise its right to pay principal on certain debt securities held by the Fund later than expected. This will cause the value of the security, and the Fund’s NAV, to decrease, and the Fund may lose opportunities to invest in higher yielding securities.</div> <div style="margin-top: 6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div>•Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies. <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> <div style="margin-top: 6pt;">High Portfolio Turnover Risk is the risk that active and frequent trading of the Fund’s portfolio securities may result in increased transaction costs to the Fund, including brokerage commissions, dealer mark-ups and other transaction costs, which could reduce the Fund’s return.</div> <div style="margin-top: 6pt;">Interest Rate/Maturity Risk is the risk that the value of the Fund’s fixed-income assets will decline because of rising interest rates. In general, securities with longer maturities or durations are more sensitive to interest rate changes. Changing interest rates, including rates that fall below zero, may have unpredictable effects on the markets and the Fund’s investments, may result in heightened market volatility, may impact the liquidity of fixed-income securities and of the Fund, and may detract from Fund performance. A low or negative interest rate environment could cause the Fund’s earnings to fall below the Fund’s expense ratio, resulting in a negative yield and a decline in the Fund’s share price. An increase in interest rates may cause investors to move out of fixed incomes securities on a large scale, which could adversely affect the price of fixed income securities, lead to heightened volatility in the fixed-income markets and may adversely affect the liquidity of certain fixed-income investments.</div> <div style="margin-top: 6pt;">Liquidity Risk is the risk that certain portfolio securities may be less liquid than others, which may make them difficult or impossible to sell at the time and the price that the Fund would like, adversely affecting the value of the Fund’s investments and its returns. Illiquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. Liquidity Risk may result from the lack of an active market, reduced number and capacity of traditional market participants to make a market in fixed income securities, and may be magnified in a rising interest rate environment or other </div> <div style="line-height: 11.90pt; margin-top: 0.00pt; text-align: left;">circumstances where investor redemptions from fixed income funds may be higher than normal, causing increased supply in the market due to selling activity. The market for certain investments may become illiquid under adverse market or economic conditions independent of any specific adverse changes in the conditions of a particular issuer. In such cases, the Fund, due to limitations on investments in illiquid securities and/or purchasing and selling such investments, may be unable to achieve a high degree of correlation with the Underlying Index. Additionally, in adverse market conditions, the Fund’s market price may begin to reflect illiquidity or pricing uncertainty of the Fund’s portfolio securities. This could lead to the Fund’s shares trading at a price that is higher or lower than the Fund’s NAV. At times, such differences may be significant.</div> <div style="margin-top: 6pt;">Rule 144A Securities Risk is the risk that limitations on the resale of Rule 144A securities may have an adverse effect on their marketability and may prevent the Fund from disposing of them promptly at reasonable prices. There can be no assurance that an active trading market will exist at any time for such securities. Transaction costs may be higher for Rule 144A securities, and such securities may be difficult to value and may have significant volatility.</div> <div style="margin-top: 6pt;">Foreign Securities Risk is the risk that investing in foreign (non-U.S.) securities may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies, due to less liquid markets and adverse economic, political, diplomatic, financial, and regulatory factors. Foreign governments may impose limitations on foreigners’ ownership of interests in local issuers, restrictions on the ability to repatriate assets, and may also impose taxes. Any of these events could cause the value of the Fund’s investments to decline. Foreign banks, agents and securities depositories that hold the Fund’s foreign assets may be subject to little or no regulatory oversight over, or independent evaluation, of their operations. Additional costs associated with investments in foreign securities may include higher custodial fees than those applicable to domestic custodial arrangements and transaction costs of foreign currency conversions. Unless the Fund has hedged its foreign currency exposure, foreign securities risk also involves the risk of negative foreign currency rate fluctuations, which may cause the value of securities denominated in such foreign currency (or other instruments through which the Fund has exposure to foreign currencies) to decline in value. Currency exchange rates may fluctuate significantly over short periods of time. Currency hedging strategies, if used, are not always successful. For instance, forward foreign </div> <div style="line-height: 11.90pt; margin-top: 0.00pt; text-align: left;">currency exchange contracts, if used by the Fund, could reduce performance if there are unanticipated changes in currency exchange rates.</div> <div style="margin-top: 6pt;">Prepayment (or Call) Risk is the risk that an issuer could exercise its right to pay principal on callable debt securities held by the Fund earlier than expected. Issuers may be more likely to prepay when interest rates fall, when credit spreads change, or when an issuer’s credit quality improves. If this happens, the Fund will not benefit from the rise in the market price of the securities that normally accompanies a decline in interest rates, and will be forced to reinvest prepayment proceeds in lower yielding securities, which may reduce the Fund’s returns. The Fund may also lose any premium it paid to purchase the securities.</div> <div style="margin-top: 6pt;">TBA Transactions Risk is the risk of loss if the securities received are less favorable than what was anticipated by the Fund when entering into the TBA transaction. TBA transactions also involve the risk that the counterparty will fail to deliver the securities, exposing the Fund to further losses. Default or bankruptcy of a counterparty to a TBA transaction would expose the Fund to possible losses because of adverse market action, expenses or delays in connection with the purchase or sale of the pools of mortgage pass-through securities specified in the TBA transaction. Whether or not the Fund takes delivery of the securities at the termination date of a TBA transaction, the Fund will nonetheless be exposed to changes in the value of the underlying investments during the term of the agreement.</div> <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> <div style="margin-top: 6pt;">Valuation Risk is the risk that the sale price the Fund could receive for a portfolio security may differ from the Fund’s valuation of the security, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. In addition, the value of the securities in the Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the periods in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (12/31/2023): 13.91% </div> <div style="margin-top: 6pt;">Worst Quarter (6/30/2022): -12.95%</div> Best Quarter 2023-12-31 0.1391 Worst Quarter 2022-06-30 -0.1295 Average Annual Total Returns (for the periods ended December 31, 2024) -0.0100 -0.0117 0.0296 2015-09-23 -0.0313 -0.0312 0.0101 -0.0059 -0.0154 0.0152 0.0125 -0.0033 0.0135 -0.0195 -0.0184 0.0275 -0.0066 -0.0051 0.0364 In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the Bloomberg Long U.S. Corporate Bond Index to the Bloomberg U.S. Aggregate Bond Index. The Fund will continue to compare its performance to the Bloomberg Long U.S. Corporate Bond Index, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® High Yield Value-Scored Bond Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Northern Trust High Yield Value-Scored US Corporate Bond IndexSM (the “Underlying Index”).</div> Fees and Expenses of the Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0037 0.0000 0.0001 0.0038 -0.0001 0.0037 March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 38 121 212 479 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 118% of the average value of its portfolio. 1.18 Principal Investment Strategies <div style="margin-top: 6pt;">The Underlying Index is designed to reflect the performance of a diversified universe of high yield, U.S.-dollar denominated bonds of companies exhibiting favorable fundamental qualities, market valuations and liquidity, as defined by NTI’s proprietary scoring models. The securities included in the Underlying Index are a subset of the securities included in the Northern Trust High Yield US Corporate Bond IndexSM (the “Parent Index”), which is a market-capitalization weighted index comprised of U.S. dollar-denominated high yield corporate bonds. </div> <div style="margin-top: 6pt;">The Underlying Index begins with the Parent Index and then follows a rules-based methodology to select and weight securities, subject to certain constraints, to optimize exposure to a proprietary value score, credit score, and liquidity score, each as determined by NTI acting in its capacity as index provider (“Index Provider”). </div> <div style="margin-top: 6pt;">The core components of the proprietary value score and proprietary credit score are based on quantitative rankings of various metrics obtained from company filings and recent price activity. The value score has multiple components, including: (a) valuation (e.g., to assess the relative </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">value of the security versus other similar securities); (b) spread analysis (e.g., to assess the risk/return trade-off associated with each security versus other similar securities); and (c) solvency (e.g., to assess the corporation’s short term and long term solvency and also its risk of default). The credit score has three components: (i) management expertise (e.g., corporate finance activities); (ii) profitability (e.g., reliability and sustainability of financial performance); and (iii) solvency. The core components of the proprietary liquidity score are based on a quantitative ranking of security characteristics obtained from company filings. Examples of data sets utilized to determine the liquidity score include: (x) time to maturity (e.g., time until the security reaches its maturity date as measured in in years); (y) total issuer debt outstanding (e.g., the sum of all debt outstanding for a single corporate issuer); and (z) time since original issuance (e.g., the time that has elapsed since the security was originally issued as measured in years). The primary objective of the optimization process is to maximize exposure to the value score relative to the Underlying Index's eligible universe. In addition, the optimization process also includes issuer level, sector, effective duration, low credit and liquidity score, duration band, and turnover constraints to seek to manage systematic risk. </div> <div style="margin-top: 6pt;">The inception date of the Underlying Index was April 30, 2018. As of December 31, 2024, there were 1167 issues in the Underlying Index. The Underlying Index is reconstituted monthly. The Fund generally reconstitutes its portfolio in accordance with the Underlying Index. </div> <div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. </div> <div style="margin-top: 6pt;">NTI intends to use representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">The Fund generally will invest under normal circumstances at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of its Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts and options on futures, to-be-announced (“TBA”) transactions, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div> <div style="margin-top: 6pt;">The Underlying Index is created and sponsored by NTI, as the Index Provider. NTI also serves as the investment adviser to the Fund. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div> <div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received). </div> <div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the industrials sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time. </div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the industrials sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time. Principal Risks <div style="margin-top: 6pt;">High Yield Securities Risk is the risk that the Fund will be subject to greater credit risk, price volatility and risk of loss than if it invested primarily in investment grade securities, </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">which can adversely impact the Fund’s return and NAV. High yield securities are considered highly speculative and are subject to increased risk of an issuer’s inability to make principal and interest payments. The Underlying Index is designed to be comprised of securities with the potential for higher yields as compared to the overall high yield corporate bond market. As such, the Fund is expected to exhibit greater sensitivity to market fluctuations.</div> <div style="margin-top: 6pt;">Distressed Securities Risk is the substantial risk of investing in distressed securities that is in addition to the risks of investing in non-investment grade securities generally. NTI defines securities issued by companies whose financial condition is troubled or uncertain and that may be involved in bankruptcy proceedings, reorganizations or financial restructurings as “distressed securities.” Distressed securities are speculative and involve a substantial risk that principal will not be paid. In addition, the Fund will generally not receive interest payments on the distressed securities and may incur costs to protect its investment. These securities may present a substantial risk of default. The Fund may incur additional expenses to the extent it is required to seek recovery upon a default in the payment of principal of or interest on its portfolio holdings. In any reorganization or liquidation proceeding relating to a portfolio company, the Fund may lose its entire investment or may be required to accept cash or securities with a value less than its original investment. Distressed securities and any securities received in an exchange for such securities may be subject to restrictions on resale.</div> <div style="margin-top: 6pt;">Substantial Volatility Risk is the risk that the value of the securities in the Fund’s portfolio may fluctuate, sometimes rapidly and unpredictably at a greater level than the overall market. There is a risk that the Fund could have substantial volatility.</div> <div style="margin-top: 6pt;">Value Score Risk is the risk that the Fund’s investment in companies whose securities are believed to be undervalued will not appreciate in value as anticipated. Although the Underlying Index is designed to measure a portfolio of bonds of companies with the potential for higher yields and less risk of insolvency relative to the Parent Index, there is no assurance that the Underlying Index or Fund will be comprised of such securities. Accordingly, the Fund may be subject to greater credit risk, price volatility and risk of loss relative to the Parent Index.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> <div style="-sec-ix-redline:true;"> <div style="line-height: 12.10pt; margin-left: 14.97pt; margin-top: 5.71pt; text-align: left;"> <div style="margin-top: 6pt;">•Industrials Sector Risk is the risk that companies in the industrials sector may be significantly affected by, among other things, worldwide economic growth, supply and demand for specific products and services, rapid technological developments, international political and economic developments, environmental issues, and tax and governmental regulatory policies.</div> </div> </div> <div style="margin-top: 6pt;">Income Risk is the risk that the Fund’s income may decline when interest rates fall. This decline can occur because the Fund must invest in lower-yielding bonds as bonds in its portfolio mature, bonds in the Underlying Index are substituted or the Fund otherwise needs to purchase additional bonds.</div> <div style="margin-top: 6pt;">Credit (or Default) Risk is the risk that the inability or unwillingness of an issuer or guarantor of a fixed-income security, or a counterparty to a TBA, repurchase or other transaction, to meet its payment or other financial obligations will adversely affect the value of the Fund’s investments and its returns. The credit quality of a debt security or of the issuer of a debt security held by the Fund could deteriorate rapidly, which may impair the Fund’s liquidity or cause a deterioration in the Fund’s NAV. The Fund could also be delayed or hindered in its enforcement of rights against an issuer, guarantor or counterparty. The degree of credit risk depends on the issuer’s or counterparty’s financial condition and on the terms of the securities.</div> <div style="margin-top: 6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;"> or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase.</div> <div style="margin-top: 6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="margin-top: 6pt;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">(“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund's holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top: 6pt;">Debt Extension Risk is the risk that when interest rates rise an issuer will exercise its right to pay principal on certain debt securities held by the Fund later than expected. This will cause the value of the security, and the Fund’s NAV, to decrease, and the Fund may lose opportunities to invest in higher yielding securities.</div> <div style="margin-top: 6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div> •Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies. <div style="margin-top: 6pt;">High Portfolio Turnover Risk is the risk that active and frequent trading of the Fund’s portfolio securities may result in increased transaction costs to the Fund, including brokerage commissions, dealer mark-ups and other transaction costs, which could reduce the Fund’s return.</div> <div style="margin-top: 6pt;">Interest Rate/Maturity Risk is the risk that the value of the Fund’s fixed-income assets will decline because of rising interest rates. In general, securities with longer maturities or durations are more sensitive to interest rate changes. Changing interest rates, including rates that fall below zero, </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">may have unpredictable effects on the markets and the Fund’s investments, may result in heightened market volatility, may impact the liquidity of fixed-income securities and of the Fund, and may detract from Fund performance. A low or negative interest rate environment could cause the Fund’s earnings to fall below the Fund’s expense ratio, resulting in a negative yield and a decline in the Fund’s share price. An increase in interest rates may cause investors to move out of fixed incomes securities on a large scale, which could adversely affect the price of fixed income securities, lead to heightened volatility in the fixed-income markets and may adversely affect the liquidity of certain fixed-income investments.</div> <div style="margin-top: 6pt;">Liquidity Risk is the risk that certain portfolio securities may be less liquid than others, which may make them difficult or impossible to sell at the time and the price that the Fund would like, adversely affecting the value of the Fund’s investments and its returns. Illiquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. Liquidity Risk may result from the lack of an active market, reduced number and capacity of traditional market participants to make a market in fixed income securities, and may be magnified in a rising interest rate environment or other circumstances where investor redemptions from fixed income funds may be higher than normal, causing increased supply in the market due to selling activity. The market for certain investments may become illiquid under adverse market or economic conditions independent of any specific adverse changes in the conditions of a particular issuer. In such cases, the Fund, due to limitations on investments in illiquid securities and/or purchasing and selling such investments, may be unable to achieve a high degree of correlation with the Underlying Index. Additionally, in adverse market conditions, the Fund’s market price may begin to reflect illiquidity or pricing uncertainty of the Fund’s portfolio securities. This could lead to the Fund’s shares trading at a price that is higher or lower than the Fund’s NAV. At times, such differences may be significant.</div> <div style="margin-top: 6pt;">Foreign Securities Risk is the risk that investing in foreign (non-U.S.) securities may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies, due to less liquid markets and adverse economic, political, diplomatic</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">, financial, and regulatory factors. Foreign governments may impose limitations on foreigners’ ownership of interests in local issuers, restrictions on the ability to repatriate assets, and may also impose taxes. Any of these events could cause the value of the Fund’s investments to decline. Foreign banks, agents and securities depositories that hold the Fund’s foreign assets may be subject to little or no regulatory oversight over, or independent evaluation, of their operations. Additional costs associated with investments in foreign securities may include higher custodial fees than those applicable to domestic custodial arrangements and transaction costs of foreign currency conversions. Unless the Fund has hedged its foreign currency exposure, foreign securities risk also involves the risk of negative foreign currency rate fluctuations, which may cause the value of securities denominated in such foreign currency (or other instruments through which the Fund has exposure to foreign currencies) to decline in value. Currency exchange rates may fluctuate significantly over short periods of time. Currency hedging strategies, if used, are not always successful. For instance, forward foreign currency exchange contracts, if used by the Fund, could reduce performance if there are unanticipated changes in currency exchange rates.</div> <div style="margin-top: 6pt;">Prepayment (or Call) Risk is the risk that an issuer could exercise its right to pay principal on callable debt securities held by the Fund earlier than expected. Issuers may be more likely to prepay when interest rates fall, when credit spreads change, or when an issuer’s credit quality improves. If this happens, the Fund will not benefit from the rise in the market price of the securities that normally accompanies a decline in interest rates, and will be forced to reinvest prepayment proceeds in lower yielding securities, which may reduce the Fund’s returns. The Fund may also lose any premium it paid to purchase the securities.</div> <div style="margin-top: 6pt;">TBA Transactions Risk is the risk of loss if the securities received are less favorable than what was anticipated by the Fund when entering into the TBA transaction. TBA transactions also involve the risk that the counterparty will fail to deliver the securities, exposing the Fund to further losses. Default or bankruptcy of a counterparty to a TBA transaction would expose the Fund to possible losses because of adverse market action, expenses or delays in connection with the purchase or sale of the pools of mortgage pass-through securities specified in the TBA transaction.</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;"> Whether or not the Fund takes delivery of the securities at the termination date of a TBA transaction, the Fund will nonetheless be exposed to changes in the value of the underlying investments during the term of the agreement.</div> <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> <div style="margin-top: 6pt;">Valuation Risk is the risk that the sale price the Fund could receive for a portfolio security may differ from the Fund’s valuation of the security, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. In addition, the value of the securities in the Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the periods in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (6/30/2020): 11.06% </div> <div style="margin-top: 6pt;">Worst Quarter (3/31/2020): -14.42%</div> Best Quarter 2020-06-30 0.1106 Worst Quarter 2020-03-31 -0.1442 Average Annual Total Returns (for the periods ended December 31, 2024) 0.0770 0.0393 0.0469 2018-07-17 0.0417 0.0085 0.0155 0.0448 0.0164 0.0219 0.0204 0.0006 0.0160 0.0820 0.0404 0.0481 0.0875 0.0549 0.0606 In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the ICE BofA® US High Yield Index to the Bloomberg Universal Index. The Fund will continue to compare its performance to the ICE BofA® US High Yield Index, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may dif</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">fer from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® ESG & Climate Investment Grade Corporate Core Index Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Northern Trust ESG & Climate Investment Grade U.S. Corporate Core IndexSM (the “Underlying Index”).</div> Fees and Expenses of the Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay eachyear as a percentage of the value of your investment) 0.0012 0.0000 0.0001 0.0013 -0.0001 0.0012 March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The </div> <div style="line-height: 12.80pt; margin-top: 0.00pt; text-align: left;">Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 12 41 72 165 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 41% of the average value of its portfolio. 0.41 Principal Investment Strategies <div style="margin-top: 6pt;">The Underlying Index, administered by NTI in its capacity as index provider (the “Index Provider”), is designed to reflect the performance of a selection of U.S.-dollar-denominated corporate bonds issued by companies that exhibit certain environmental, social and governance (“ESG”) characteristics in the aggregate, while also seeking to provide exposure to US dollar-denominated corporate bonds, i.e., the constituents in the Northern Trust Investment Grade U.S. Corporate Bond IndexSM (the “Eligible Universe”). The Northern Trust Investment Grade U.S. Corporate Bond IndexSM is a market-capitalization weighted index comprised of US dollar-denominated corporate bonds that (a) are publicly issued in the United States and registered with the SEC or eligible for resale under Rule 144A under the Securities Act of 1933, with or without registration rights, (b) are rated investment grade (i.e., rated at the time of inclusion in the Eligible Universe within the top four ratings categories by a Nationally Recognized Statistical Rating Organization (“NRSRO”)), and (c) have, at each rebalance, (i) a final time to stated maturity of at least one year and (ii) an outstanding principal balance of at least $250 million. The </div> <div style="line-height: 12.80pt; margin-top: 0.00pt; text-align: left;">Fund does not have any portfolio maturity limitation and may invest its assets from time to time in instruments with varying maturities. </div> <div style="margin-top: 6pt;">The Underlying Index starts by excluding certain companies from the Eligible Universe that, based on third-party data, are determined to have certain levels of controversial business involvement or behavior, including in tobacco, weaponry, thermal coal, unconventional oil and gas, and for-profit prisons, or to have caused, contributed to or are linked to certain violations of international norms and standards. Such exclusions are based on percentage of revenue thresholds for certain categories (e.g., those that receive significant revenue from production, retail and distribution of civilian weapons) and categorical exclusions for others (e.g., tobacco producers). The above-described exclusionary screens are applied with each reconstitution of the Underlying Index. The Index Provider may modify this list of excluded companies at any time, at its own discretion. </div> <div style="margin-top: 6pt;">The Underlying Index next applies an optimization process to minimize variance to the Eligible Universe while also targeting certain ESG characteristics, which is designed to produce an index that, relative to the Eligible Universe: (a) has an aggregate higher scoring of certain ESG characteristics, as measured by the Northern Trust ESG Vector Score (“ESG Vector Score”) described below, (b) improves the carbon risk rating, as measured by certain carbon-related risk metrics, and (c) decreases the weighted average carbon intensity and potential emissions. </div> <div style="margin-top: 6pt;">The ESG Vector Score is designed to rank companies based on their management of and exposure to material ESG metrics as defined by the Sustainability Accounting Standards Board (“SASB”) Standards. In addition, the Index Provider uses available data from Institutional Shareholder Services ESG Solutions to assess carbon emissions intensity, carbon reserves and a carbon risk rating. Carbon emissions intensity measures (i) direct greenhouse gas emissions from sources controlled or owned by the company (e.g., emissions associated with fuel combustion in boilers, furnaces, or vehicles); and (ii) indirect greenhouse gas emissions associated with the purchase of electricity, steam, heat or cooling against the company. Carbon reserves measure the total estimated greenhouse gas emissions attributable to a company’s fossil fuel reserve assets. The carbon risk rating provides an assessment of a company’s ability to mitigate the risks of transition to a lower carbon economy based on its specific baseline carbon risk exposure. </div> <div style="line-height: 12.80pt; margin-top: 0.00pt; text-align: left;">In the event that metrics or other data used to construct the ESG Vector Score as well as carbon emissions intensity, carbon reserves and/or the carbon risk rating are not available or otherwise deemed unreliable, NTI may make reasonable estimates or otherwise exercise its discretion to implement the optimization process. </div> <div style="margin-top: 6pt;">Notwithstanding the optimization process, it is possible that the Underlying Index will include (and therefore the Fund could invest in) securities that, individually, have a lower ESG Vector Score, lower carbon risk rating, or higher emissions relative to the weighted average of the Eligible Universe. The optimization process also includes sector, country, turnover, issuer and constituent constraints so that these characteristics in the Underlying Index vary within acceptable bands relative to the Eligible Universe.</div> <div style="margin-top: 6pt;">The Underlying Index is a new index with an inception date of July 30, 2021. As of December 31, 2024, there were 3698 issues in the Underlying Index. The Underlying Index is reconstituted monthly under normal market conditions. The Fund generally reconstitutes its portfolio in accordance with the Underlying Index. </div> <div style="margin-top: 6pt;">NTI uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. </div> <div style="margin-top: 6pt;">NTI uses a representative sampling strategy to manage the Fund. “Representative sampling” is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. </div> <div style="margin-top: 6pt;">Under normal circumstances, the Fund will invest at least 80% of its total assets (exclusive of collateral held from securities lending) in the securities of the Underlying Index. The Fund may also invest up to 20% of its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts and options on futures contracts, to-be-announced (“TBA”) transactions, as well as securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. </div> <div style="line-height: 12.80pt; margin-top: 0.00pt; text-align: left;">The Underlying Index is created and sponsored by NTI, as the Index Provider. NTI also serves as the investment adviser to the Fund. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. </div> <div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received).</div> <div style="margin-top: 6pt;">Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the financial sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time.</div> Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. As of December 31, 2024, the Underlying Index was concentrated in the financial sector. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time. Principal Risks <div style="margin-top: 6pt;">ESG Investment Risk is the risk that because the Index Provider includes and excludes issuers and assigns weights to issuers in the Underlying Index by applying non-financial factors, the Fund may underperform the broader equity market or other funds that do or do not use ESG factors, scores, or screens in their securities selection process, or use a different ESG methodology. The ESG methodology of the Underlying Index will affect the Fund’s exposure to certain companies and sectors and may adversely affect the Fund’s performance depending on whether such companies and sectors are in or out of favor. Although the Underlying Index is designed to measure a portfolio of companies with certain ESG characteristics, there is no assurance that every security in the Underlying Index or Fund will have ESG characteristics or that companies that have historically exhibited such characteristics will continue to exhibit such characteristics. There is also the risk that the Fund may have indirect exposure to companies that have been excluded from the Underlying Index through its use of certain derivative instruments. </div> <div style="margin-top: 6pt;">Currently, there is a lack of common industry standards relating to the development and application of ESG criteria, which may make it difficult to compare the Fund’s principal investment strategies with the investment strategies of other funds that integrate certain ESG criteria. The subjective value that investors may assign to certain types of ESG characteristics may differ substantially from that of the assessment by the Index Provider or a data provider. </div> <div style="line-height: 12.80pt; margin-top: 0.00pt; text-align: left;">Investors can differ in their views of what constitutes positive or negative ESG characteristics. As a result, the Fund may invest in companies that do not reflect the beliefs and values of any particular investor. A company included in the Underlying Index may not exhibit positive or favorable ESG characteristics. The companies selected by the Index Provider as demonstrating certain ESG characteristics may not be the same companies selected by other index providers or investment managers as exhibiting those characteristics. </div> <div style="margin-top: 6pt;">The Index Provider relies on various sources of information regarding an issuer, including information that may be based on assumptions and estimates. ESG information from third-party data providers may be incomplete, inaccurate or unavailable. Neither the Fund nor NTI can offer assurances that the Underlying Index’s methodology or sources of information will provide an accurate assessment of the issuers of the securities included in the Fund’s Underlying Index. The Index Provider uses third-party data that it believes to be reliable, but it does not guarantee the accuracy of such third-party data. Data can vary across providers or within industries. ESG standards differ by region and industry, and a company’s ESG practices or the Index Provider’s or data providers’ assessment of a company’s ESG practices may change over time. Regulatory changes or interpretations regarding the definitions and/or use of ESG criteria could have a material adverse effect on the Fund’s ability to invest in accordance with its investment policies and/or achieve its investment objective.</div> <div style="margin-top: 6pt;">Corporate Bond Risk is the risk the Fund faces because it invests primarily in bonds issued by corporations. Corporate debt securities are subject to the risk of the issuer’s inability to meet principal and interest payments on the obligation and may also be subject to price volatility due to such factors as interest rate sensitivity, market perception of the creditworthiness of the issuer and general market liquidity. When interest rates rise, the value of corporate debt can be expected to decline. Debt securities with longer maturities tend to be more sensitive to interest rate movements than those with shorter maturities.</div> <div style="margin-top: 6pt;">Credit (or Default) Risk is the risk that the inability or unwillingness of an issuer or guarantor of a fixed-income security, or a counterparty to a TBA, repurchase or other transaction, to meet its payment or other financial obligations will adversely affect the value of the Fund’s investments and its returns. The credit quality of a debt security </div> <div style="line-height: 12.80pt; margin-top: 0.00pt; text-align: left;">or of the issuer of a debt security held by the Fund could deteriorate rapidly, which may impair the Fund’s liquidity or cause a deterioration in the Fund’s NAV. The Fund could also be delayed or hindered in its enforcement of rights against an issuer, guarantor or counterparty. The degree of credit risk depends on the issuer’s or counterparty’s financial condition and on the terms of the securities.</div> <div style="margin-top: 6pt;">Interest Rate/Maturity Risk is the risk that the value of the Fund’s fixed-income assets will decline because of rising interest rates. In general, securities with longer maturities or durations are more sensitive to interest rate changes. Changing interest rates, including rates that fall below zero, may have unpredictable effects on the markets and the Fund’s investments, may result in heightened market volatility, may impact the liquidity of fixed-income securities and of the Fund, and may detract from Fund performance. A low or negative interest rate environment could cause the Fund’s earnings to fall below the Fund’s expense ratio, resulting in a negative yield and a decline in the Fund’s share price. An increase in interest rates may cause investors to move out of fixed incomes securities on a large scale, which could adversely affect the price of fixed income securities, lead to heightened volatility in the fixed-income markets and may adversely affect the liquidity of certain fixed-income investments.</div> <div style="margin-top: 6pt;">Debt Extension Risk is the risk that when interest rates rise an issuer will exercise its right to pay principal on certain debt securities held by the Fund later than expected. This will cause the value of the security, and the Fund’s NAV, to decrease, and the Fund may lose opportunities to invest in higher yielding securities.</div> <div style="margin-top: 6pt;">Prepayment (or Call) Risk is the risk that an issuer could exercise its right to pay principal on callable debt securities held by the Fund earlier than expected. Issuers may be more likely to prepay when interest rates fall, when credit spreads change, or when an issuer’s credit quality improves. If this happens, the Fund will not benefit from the rise in the market price of the securities that normally accompanies a decline in interest rates, and will be forced to reinvest prepayment proceeds in lower yielding securities, which may reduce the Fund’s returns. The Fund may also lose any premium it paid to purchase the securities.</div> <div style="margin-top: 6pt;">Income Risk is the risk that the Fund’s income may decline when interest rates fall. This decline can occur because the Fund must invest in lower-yielding bonds as bonds in its portfolio mature, bonds in the Underlying Index are substituted or the Fund otherwise needs to purchase additional bonds.</div> <div style="line-height: 12.80pt; margin-top: 0.00pt; text-align: left;">Foreign Securities Risk is the risk that investing in foreign (non-U.S.) securities may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies, due to less liquid markets and adverse economic, political, diplomatic, financial, and regulatory factors. Foreign governments may impose limitations on foreigners’ ownership of interests in local issuers, restrictions on the ability to repatriate assets, and may also impose taxes. Any of these events could cause the value of the Fund’s investments to decline. Foreign banks, agents and securities depositories that hold the Fund’s foreign assets may be subject to little or no regulatory oversight over, or independent evaluation, of their operations. Additional costs associated with investments in foreign securities may include higher custodial fees than those applicable to domestic custodial arrangements and transaction costs of foreign currency conversions. Unless the Fund has hedged its foreign currency exposure, foreign securities risk also involves the risk of negative foreign currency rate fluctuations, which may cause the value of securities denominated in such foreign currency (or other instruments through which the Fund has exposure to foreign currencies) to decline in value. Currency exchange rates may fluctuate significantly over short periods of time. Currency hedging strategies, if used, are not always successful. For instance, forward foreign currency exchange contracts, if used by the Fund, could reduce performance if there are unanticipated changes in currency exchange rates.</div> <div style="margin-top: 6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums</div> <div style="line-height: 12.80pt; margin-top: 0.00pt; text-align: left;"> or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase.</div> <div style="margin-top: 6pt;">Liquidity Risk is the risk that certain portfolio securities may be less liquid than others, which may make them difficult or impossible to sell at the time and the price that the Fund would like, adversely affecting the value of the Fund’s investments and its returns. Illiquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. Liquidity Risk may result from the lack of an active market, reduced number and capacity of traditional market participants to make a market in fixed income securities, and may be magnified in a rising interest rate environment or other circumstances where investor redemptions from fixed income funds may be higher than normal, causing increased supply in the market due to selling activity. The market for certain investments may become illiquid under adverse market or economic conditions independent of any specific adverse changes in the conditions of a particular issuer. In such cases, the Fund, due to limitations on investments in illiquid securities and/or purchasing and selling such investments, may be unable to achieve a high degree of correlation with the Underlying Index. Additionally, in adverse market conditions, the Fund’s market price may begin to reflect illiquidity or pricing uncertainty of the Fund’s portfolio securities. This could lead to the Fund’s shares trading at a price that is higher or lower than the Fund’s NAV. At times, such differences may be significant.</div> <div style="margin-top: 6pt;">Rule 144A Securities Risk is the risk that limitations on the resale of Rule 144A securities may have an adverse effect on their marketability and may prevent the Fund from disposing of them promptly at reasonable prices. There can be no assurance that an active trading market will exist at any time for such securities. Transaction costs may be higher for Rule 144A securities, and such securities may be difficult to value and may have significant volatility.</div> <div style="margin-top: 6pt;">Index Risk is the risk that the Fund would not necessarily buy or sell a security unless that security is added to or removed from, respectively, the Underlying Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Underlying Index. Additionally, the Fund rebalances and/or </div> <div style="line-height: 12.80pt; margin-top: 0.00pt; text-align: left;">reconstitutes its portfolio in accordance with the Underlying Index, and, therefore, any changes to the Underlying Index’s rebalance and/or reconstitution schedule will result in corresponding changes to the Fund’s rebalance and/or reconstitution schedule.</div> <div style="margin-top: 6pt;">Tracking Error Risk is the risk that the Fund’s performance may vary from the performance of the Underlying Index as a result of creation and redemption activity, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund's ability to adjust its exposure to required levels in order to track its Index or cause delays in the Underlying Index's rebalancing schedule. During any such delay, it is possible that the Underlying Index, and, in turn, the Fund will deviate from the Underlying Index's stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.</div> <div style="margin-top: 6pt;">Sampling Risk is the risk that the Fund’s use of a representative sampling approach may not work as intended and result in increased tracking error because the securities selected for the Fund in the aggregate may vary from the investment profile of the Underlying Index. Additionally, the use of a representative sampling approach may result in the Fund holding a smaller number of securities than the Underlying Index, and, as a result, an adverse development to an issuer of securities that the Fund holds could result in a greater decline in NAV than would be the case if the Fund held all of the securities in the Underlying Index.</div> <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting.</div> <div style="margin-top: 6pt;">Calculation Methodology Risk is the risk that the Underlying Index’s calculation methodology or sources of information may not provide an accurate assessment of </div> <div style="line-height: 12.80pt; margin-top: 0.00pt; text-align: left;">included issuers or correct valuation of securities, nor is the availability or timeliness of the production of the Underlying Index guaranteed. A security included in the Underlying Index may not exhibit the characteristic or provide the specific exposure for which it was selected and consequently a Fund’s holdings may not exhibit returns consistent with that characteristic or exposure.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV. </div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market prices of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity, or the perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top: 6pt;">Concentration Risk is the risk that, if the Fund is concentrated in a particular industry or group of industries, the Fund is likely to present more risks than a fund that is broadly diversified over several industries or groups of industries. Compared to the broad market, an individual industry may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock or regulatory changes.</div> •Financial Sector Risk is the risk that the financial sector can be significantly affected by changes in interest rates, government regulation, the rate of corporate and consumer debt defaulted, price competition, and the availability and cost of capital, among other factors. <div style="margin-top: 6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity </div> <div style="line-height: 12.80pt; margin-top: 0.00pt; text-align: left;">that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div> •Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Options Contracts Risk Options contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the investment adviser’s ability to predict correctly future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the investment adviser, thus limiting the ability to implement the Fund’s strategies. <div style="margin-top: 6pt;">New Fund Risk is the risk that the Fund will not grow to or maintain an economically viable size, in which case it may experience greater tracking error to its Underlying Index than it otherwise would at higher asset levels, or it could ultimately liquidate without shareholder approval. The timing of such liquidation may not be favorable and could have negative tax consequences for shareholders. From time to time, an Authorized Participant, a third-party investor, the Fund’s adviser or an affiliate of the Fund’s adviser, may invest in the Fund and hold its investment for a specific period of time in order to facilitate commencement of the Fund’s operations or for the Fund to achieve size or scale. There can be no assurance that any such entity would not redeem its investment or that the size of the Fund would be maintained at such levels, which could negatively impact the Fund. The Fund’s Distributor does not maintain a secondary market in the shares.</div> <div style="margin-top: 6pt;">TBA Transactions Risk is the risk of loss if the securities received are less favorable than what was anticipated by the Fund when entering into the TBA transaction. TBA transactions</div> <div style="line-height: 12.80pt; margin-top: 0.00pt; text-align: left;"> also involve the risk that the counterparty will fail to deliver the securities, exposing the Fund to further losses. Default or bankruptcy of a counterparty to a TBA transaction would expose the Fund to possible losses because of adverse market action, expenses or delays in connection with the purchase or sale of the pools of mortgage pass-through securities specified in the TBA transaction. Whether or not the Fund takes delivery of the securities at the termination date of a TBA transaction, the Fund will nonetheless be exposed to changes in the value of the underlying investments during the term of the agreement.</div> <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> <div style="margin-top: 6pt;">Valuation Risk is the risk that the sale price the Fund could receive for a portfolio security may differ from the Fund’s valuation of the security, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. In addition, the value of the securities in the Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com. </div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year, (B) how the Fund’s average annual returns compare with those of a broad measure of market performance, and (C) an additional index with characteristics relevant to the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the periods shown in the bar chart above: </div> <div style="margin-top: 6pt;">Best Quarter (12/31/2023): 8.32% </div> <div style="margin-top: 6pt;">Worst Quarter (3/31/2022): -7.45% </div> Best Quarter 2023-12-31 0.0832 Worst Quarter 2022-03-31 -0.0745 Average Annual Total Returns (for the periods ended December 31, 2024) 0.0202 -0.0268 2021-09-20 0.0013 -0.0416 0.0118 -0.0265 0.0125 -0.0252 0.0213 -0.0245 0.0235 -0.0240 In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the Bloomberg US Corporate Total Return Value Unhedged Index to the Bloomberg U.S. Aggregate Bond Index. The Fund will continue to compare its performance to the Bloomberg US Corporate Total Return Value Unhedged Index, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before </div> <div style="line-height: 12.80pt; margin-top: 0.00pt; text-align: left;">taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return beforetaxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® Ultra-Short Income Fund Investment Objective <div style="margin-top: 6pt;">The Fund seeks maximum current income consistent with the preservation of capital and liquidity.</div> Fees and Expenses of the Fund <div style="margin-top: 6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay each yearas a percentage of the value of your investment) 0.0025 0.0000 0.0001 0.0026 -0.0001 0.0025 March 1, 2026 Example <div style="margin-top: 6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 26 83 145 330 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 53% of the average value of its portfolio. 0.53 Principal Investment Strategies <div style="margin-top: 6pt;">The Fund seeks to achieve its investment objective by investing under normal circumstances at least 80% of its total assets in a portfolio of fixed-income instruments, including bonds, debt securities and other similar instruments issued by U.S. and non-U.S. public and private sector entities. Such issuers include, without limitation, U.S. and non-U.S. governments and their agencies, instrumentalities or sponsored enterprises, U.S. state and local governments and municipalities, and U.S. and non-U.S. private-sector entities, such as corporations and banks. The average portfolio duration of this Fund will vary based on The Northern Trust Company Investment Policy Committee’s forecast for interest rates and will normally not exceed one year. Duration measures the price sensitivity of a fixed-income security to changes in interest rates. Interest rate changes have a greater effect on the price of fixed-income securities with longer durations. The dollar-weighted average portfolio maturity of the Fund is normally not expected to exceed two years. </div> <div style="margin-top: 6pt;">The Fund invests in investment grade debt securities (i.e., securities that are, at the time of investment, rated within the top four rating categories by a Nationally Recognized Statistical Rating Organization (“NRSRO”) or of compa</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">rable quality as determined by NTI). The Fund may invest, without limitation, in fixed-income securities and instruments of foreign issuers in developed markets, including debt securities of foreign governments, and may invest more than 25% of its total assets in securities and instruments of issuers in a single developed market country. The Fund may invest up to 20% of its total assets in fixed-income securities and instruments of issuers in emerging markets. </div> <div style="margin-top: 6pt;">The Fund may invest, without limitation, in mortgage- or asset-backed securities, including to-be-announced (“TBAs”) transactions, and purchase and sell securities on a when-issued, delayed delivery or forward commitment basis. However, the Fund will not invest more than 10% of its total assets in non-agency mortgage or asset-backed securities. The Fund also may, without limitation, seek to obtain market exposure to the securities in which it primarily invests by entering into a series of purchase and sale contracts (such as buy backs or mortgage dollar rolls). The Fund may engage in forward foreign currency transactions for hedging purposes in order to protect against uncertainty in the level of future foreign currency exchange rates, to facilitate local settlements or to protect against currency exposure in connection with its distributions to shareholders. The Fund, however, does not expect to engage in currency transactions for speculative purposes (e.g., for potential income or capital gain). In seeking to achieve its investment objective, the Fund may invest in U.S. Treasury futures contracts, which are considered to be derivative instruments, for various purposes, including to manage duration, credit and interest rate risks, and for cash management.</div> <div style="margin-top: 6pt;">The Fund is an actively managed ETF that does not seek to replicate the performance of a specified index. The Fund may have a higher degree of portfolio turnover than funds that seek to replicate the performance of an index.</div> <div style="margin-top: 6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received).</div> <div style="margin-top: 6pt;">From time to time the Fund may focus its investments (i.e., invest more than 15% of its total assets) in one or more particular sectors. As of December 31, 2024, the Fund focused its investments in the financial sector. </div> Principal Risks <div style="margin-top: 6pt;">Management Risk is the risk that a strategy used by NTI may fail to produce the intended results or that imperfections, errors or limitations in the tools and data used by NTI may cause unintended results.</div> <div style="margin-top: 6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase.</div> <div style="margin-top: 6pt;">Cash Transactions Risk is the risk from the Fund effecting creation and redemption orders of its shares entirely for cash, rather than for in-kind securities. The Fund may have to sell portfolio securities at inopportune times in order to obtain the cash needed to meet redemption orders. This may cause the Fund to sell a security or other financial instrument and recognize a capital gain or loss that might </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">not have been incurred if it had not effected a redemption order entirely for cash. As such, investments in Fund shares may be less tax-efficient than an investment in an ETF that meets redemption orders entirely in-kind with portfolio securities. The use of all cash creation and redemption orders may also cause the Fund’s shares to trade in the secondary market at wider bid-ask spreads and/or greater premiums or discounts to the Fund’s NAV. To the extent that the maximum additional variable charge for cash creation or cash redemption transactions is insufficient to cover the transaction costs of purchasing or selling portfolio securities, the Fund’s performance could be negatively impacted.</div> <div style="margin-top: 6pt;">Foreign Securities Risk is the risk that investing in foreign (non-U.S.) securities may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies, due to less liquid markets and adverse economic, political, diplomatic, financial, and regulatory factors. Foreign governments may impose limitations on foreigners’ ownership of interests in local issuers, restrictions on the ability to repatriate assets, and may also impose taxes. Any of these events could cause the value of the Fund’s investments to decline. Foreign banks, agents and securities depositories that hold the Fund’s foreign assets may be subject to little or no regulatory oversight over, or independent evaluation, of their operations. Additional costs associated with investments in foreign securities may include higher custodial fees than those applicable to domestic custodial arrangements and transaction costs of foreign currency conversions. Unless the Fund has hedged its foreign currency exposure, foreign securities risk also involves the risk of negative foreign currency rate fluctuations, which may cause the value of securities denominated in such foreign currency (or other instruments through which the Fund has exposure to foreign currencies) to decline in value. Currency exchange rates may fluctuate significantly over short periods of time. Currency hedging strategies, if used, are not always successful. For instance, forward foreign currency exchange contracts, if used by the Fund, could reduce performance if there are unanticipated changes in currency exchange rates.</div> <div style="margin-top: 6pt;">Emerging Markets Risk is the risk that emerging markets are generally subject to greater market volatility, political, social and economic instability, uncertain trading markets and more governmental limitations on foreign investments </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">than more developed markets. In addition, companies operating in emerging markets may be subject to lower trading volumes and greater price volatility than companies in more developed markets. Emerging market economies may be based on only a few industries, may be highly vulnerable to changes in local and global trade conditions, and may suffer from extreme and volatile debt burdens or inflation rates. Companies in emerging market countries generally may be subject to less stringent regulatory, disclosure, financial reporting, accounting, auditing and recordkeeping standards than companies in more developed countries. As a result, information, including financial information, about such companies may be less available and reliable, which can impede the Fund’s ability to evaluate such companies. Securities law and the enforcement of systems of taxation in many emerging market countries may change quickly and unpredictably, and the ability to bring and enforce actions (including bankruptcy, confiscatory taxation, expropriation, nationalization of a company’s assets, restrictions on foreign ownership of local companies, restrictions on withdrawing assets from the country, protectionist measures and practices such as share blocking), or to obtain information needed to pursue or enforce such actions, may be limited. Investments in emerging market securities may be subject to additional transaction costs, delays in settlement procedures, unexpected market closures, and lack of timely information.</div> <div style="margin-top: 6pt;">Geographic Risk is the risk that if the Fund invests a significant portion of its total assets in certain issuers within the same country or geographic region, an adverse economic, business or political development affecting that country or region may affect the value of the Fund’s investments more, and the Fund's investments may be more volatile than if the Fund’s investments were not so concentrated in such country or region.</div> <div style="margin-top: 6pt;">Income Risk is the risk that the Fund’s income may decline when interest rates fall. This decline can occur because the Fund must invest in lower-yielding bonds as bonds in its portfolio mature or the Fund otherwise needs to purchase additional bonds.</div> <div style="margin-top: 6pt;">Sector Risk is the risk that companies in similar businesses may be similarly affected by particular economic or market events, which may, in certain circumstances, cause the value of securities of all companies in a particular sector of the market to decrease.</div> •Financial Sector Risk is the risk that the financial sector can be significantly affected by changes in interest rates, government regulation, the rate of corporate and consumer debt defaulted, price competition, and the availability and cost of capital, among other factors. <div style="margin-top: 6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting. This risk may be heightened because of its investments in non-U.S. securities.</div> <div style="margin-top: 6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.</div> <div style="margin-top: 6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market price of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity or perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top: 6pt;">Credit (or Default) Risk is the risk that the inability or unwillingness of an issuer or guarantor of a fixed-income security, or a counterparty to a TBA, repurchase or other transaction, to meet its payment or other financial obligations will adversely affect the value of the Fund’s investments and its returns. The credit quality of a debt security or of the issuer of a debt security held by the Fund could deteriorate rapidly, which may impair the Fund's liquidity </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">or cause a deterioration in the Fund's NAV. The Fund could also be delayed or hindered in its enforcement of rights against an issuer, guarantor or counterparty. The degree of credit risk depends on the issuer’s or counterparty’s financial condition and on the terms of the securities.</div> <div style="margin-top: 6pt;">Debt Extension Risk is the risk that when interest rates rise an issuer will exercise its right to pay principal on certain debt securities held by the Fund later than expected. This will cause the value of the security, and the Fund’s NAV, to decrease, and the Fund may lose opportunities to invest in higher yielding securities.</div> <div style="margin-top: 6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div> •Forward Foreign Currency Contracts Risk is the risk that, if forward prices increase, a loss will occur to the extent that the agreed upon purchase price of the currency exceeds the price of the currency that was agreed to be sold.•Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss. <div style="margin-top: 6pt;">Interest Rate/Maturity Risk is the risk that the value of the Fund’s fixed-income assets will decline because of rising interest rates. In general, securities with longer maturities </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">or durations are more sensitive to interest rate changes. Changing interest rates, including rates that fall below zero, may have unpredictable effects on the markets and the Fund’s investments, may result in heightened market volatility, may impact the liquidity of fixed-income securities and of the Fund, and may detract from Fund performance. A low or negative interest rate environment could cause the Fund’s earnings to fall below the Fund’s expense ratio, resulting in a negative yield and a decline in the Fund’s share price. An increase in interest rates may cause investors to move out of fixed income securities on a large scale, which could adversely affect the price of fixed income securities, lead to heightened volatility in the fixed-income markets and may adversely affect the liquidity of certain fixed-income investments. During periods when inflation rates are high or rising, or during periods of low interest rates, the Fund may be subject to a greater risk of rising interest rates.</div> <div style="margin-top: 6pt;">Leveraging Risk is the risk that certain transactions of the Fund, such as the use of when-issued, delayed delivery or forward commitment transactions and investments in forward foreign currency contracts, may give rise to leverage, causing the Fund to be more volatile than if it had not been leveraged.</div> <div style="margin-top: 6pt;">Liquidity Risk is the risk that certain portfolio securities may be less liquid or may become less liquid than others, which may make them difficult or impossible to sell at the time and the price that the Fund would like, adversely affecting the value of the Fund’s investments and its returns. Illiquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. Liquidity risk may result from the lack of an active market, reduced number and capacity of traditional market participants to make a market in fixed income securities, and may be magnified in a rising interest rate environment or other circumstances where investor redemptions from fixed income funds may be higher than normal, causing increased supply in the market due to selling activity. The market for certain investments may become illiquid under adverse market or economic conditions independent of any specific adverse changes in the conditions of a particular issuer. Additionally, in adverse market conditions, the Fund’s market price may begin to reflect illiquidity or pricing uncertainty of the </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">Fund’s portfolio securities. This could lead to the Fund’s shares trading at a price that is higher or lower than the Fund’s NAV. At times, such differences may be significant.</div> <div style="margin-top: 6pt;">Asset-Backed and Mortgage-Backed Securities Risk. Asset-backed and mortgage-backed securities may be less liquid than other bonds, and may be more sensitive than other bonds to the market’s perception of issuers and creditworthiness of payees, particularly in declining general economic conditions when concern regarding mortgagees’ ability to pay (e.g., the ability of homeowners, commercial mortgagees, consumers with student loans, automobile loans or credit card debtholders to make payments on the underlying loan pools) rises, which may result in the Fund experiencing difficulty selling or valuing these securities. In addition, these securities may not be backed by the full faith and credit of the U.S. government, have experienced extraordinary weakness and volatility at various times in recent years, and may decline quickly in the event of a substantial economic or market downturn. Those asset-backed and mortgage-backed securities that are guaranteed as to the timely payment of interest and principal by a government entity, are not guaranteed as to market price, which will fluctuate. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain asset-backed and mortgage-backed securities. </div> <div style="margin-top: 6pt;">Municipal Market Volatility Risk is the risk that the Fund may be adversely affected by volatility in the municipal market. The municipal market can be significantly affected by adverse tax, legislative, political or public health changes and the financial condition of the issuers of municipal securities.</div> <div style="margin-top: 6pt;">Prepayment (or Call) Risk is the risk that an issuer could exercise its right to pay principal on callable debt securities held by the Fund earlier than expected. Issuers may be more likely to prepay when interest rates fall, when credit spreads change, or when an issuer’s credit quality improves. If this happens, the Fund will not benefit from the rise in the market price of the securities that normally accompanies a decline in interest rates, and will be forced to reinvest prepayment proceeds in lower yielding securities, which may reduce the Fund’s returns. The Fund may also lose any premium it paid to purchase the securities.</div> <div style="margin-top: 6pt;">TBA Transactions Risk is the risk of loss if the securities received are less favorable than what was anticipated by the Fund when entering into the TBA transaction. TBA transactions also involve the risk that the counterparty will fail to deliver the securities, exposing the Fund to further losses. Default or bankruptcy of a counterparty to a TBA transaction would expose the Fund to possible losses </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">because of adverse market action, expenses or delays in connection with the purchase or sale of the pools of mortgage pass-through securities specified in the TBA transaction. Whether or not the Fund takes delivery of the securities at the termination date of a TBA transaction, the Fund will nonetheless be exposed to changes in the value of the underlying investments during the term of the agreement.</div> <div style="margin-top: 6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.</div> <div style="margin-top: 6pt;">U.S. Government Securities Risk is the risk that the U.S. government will not provide financial support to its agencies, instrumentalities or sponsored enterprises if it is not obligated to do so by law. Many U.S. government securities that may be purchased by the Fund are not backed by the full faith and credit of the United States. The maximum potential liability of the issuers of some U.S. government securities may greatly exceed their current resources, including any legal right to support from the U.S. Treasury. It is possible that the issuers of such securities will not have the funds to meet their payment obligations in the future.</div> <div style="margin-top: 6pt;">Valuation Risk is the risk that the sale price the Fund could receive for a portfolio security may differ from the Fund’s valuation of the security, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. In addition, the value of the securities in the Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top: 6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication</div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;"> of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year and (B) how the Fund’s average annual returns compare with those of a broad measure of market performance. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year and (B) how the Fund’s average annual returns compare with those of a broad measure of market performance. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top: 6pt;">For the periods in the bar chart above:</div> <div style="margin-top: 6pt;">Best Quarter (6/30/2020): 2.84%</div> <div style="margin-top: 6pt;">Worst Quarter (3/31/2020): -1.32%</div> Best Quarter 2020-06-30 0.0284 Worst Quarter 2020-03-31 -0.0132 Average Annual Total Returns (for the periods ended December 31, 2024) 0.0568 0.0264 0.0213 0.0341 0.0150 0.0124 0.0333 0.0154 0.0125 -0.0169 -0.0196 0.0015 0.0532 0.0249 0.0175 In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the Bloomberg 1-3 Month U.S. Treasury Bill Index to the Bloomberg Global Aggregate Bond Index. The Fund will continue to compare its performance to the Bloomberg 1-3 Month U.S. Treasury Bill Index, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. <div style="margin-top: 6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax </div> <div style="line-height: 13.10pt; margin-top: 0.00pt; text-align: left;">returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. FlexShares® Core Select Bond Fund Investment Objective <div style="margin-top:6pt;">The Fund seeks total return and preservation of capital.</div> Fees and Expenses of the Fund <div style="margin-top:6pt;">This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions and fees to financial intermediaries when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:</div> Annual Fund Operating Expenses (expenses that you pay each yearas a percentage of the value of your investment) 0.0035 0.0000 0.0001 0.0013 0.0049 -0.0011 0.0038 The "Total Annual Fund Operating Expenses" may not correlate to the ratio of expenses to average net assets as reported in the "Financial Highlights" section of the Prospectus, which reflects the operating expenses of the Fund and does include "Acquired Fund Fees and Expenses." March 1, 2026 Example <div style="margin-top:6pt;">The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:</div> 39 146 263 605 Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. Portfolio turnover may vary from year to year, as well as within a year. During the most recent fiscal year, the Fund’s portfolio turnover rate was 32% of the average value of its portfolio. 0.32 Principal Investment Strategies <div style="margin-top:6pt;">The Fund seeks to achieve its investment objective by investing, under normal circumstances, at least 80% of its net assets in U.S. dollar-denominated investment-grade fixed-income securities either directly or indirectly through exchange-traded funds ("ETFs") and other registered investment companies (together with ETFs, “Underlying Funds”). The Fund primarily invests in fixed-income securities of varying maturities, including bonds, debt securities and other similar instruments issued by U.S. public and U.S and non-U.S. private sector entities. Such issuers include, without limitation, U.S. governments and their agencies, instrumentalities or sponsored enterprises, and </div><div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">U.S. and non-U.S. private-sector entities, such as corporations and banks. The Fund may invest in fixed income securities of any maturity.</div><div style="margin-top:6pt;">The Fund seeks to provide attractive risk-adjusted performance by investing in a portfolio of fixed-income securities and Underlying Funds. The Fund generally adjusts its allocations to securities based on NTI’s assessment of potential changes in interest rate levels, the shape of the yield curve and credit spread relationships. The Fund also seeks to balance the potential for return and risk while emphasizing liquidity and diversification across a spectrum of U.S. dollar-denominated investment-grade fixed income securities. </div><div style="margin-top:6pt;">The Fund may invest, without limitation, in mortgage- or asset-backed securities, including to-be-announced (“TBA”) transactions, and purchase and sell securities on a when-issued, delayed delivery or forward commitment basis. The Fund also may, without limitation, seek to obtain market exposure to the securities in which it primarily invests by entering into a series of purchase and sale contracts (such as buy backs or mortgage dollar rolls).</div><div style="margin-top:6pt;">In seeking to achieve its investment objective, the Fund may invest in U.S. Treasury futures contracts, which are considered to be derivative instruments, for various purposes, including to manage duration, credit and interest rate risks, and for cash management. The Fund may take short or long positions in U.S. Treasury futures or transact in interest rate swaps. The Fund's short positions in U.S. Treasury futures are not intended to mitigate credit spread risk or other factors influencing the price of non-government bonds, which may have a greater impact than interest rates. The Fund may also invest in other interest rate futures contracts, including, but not limited to, Eurodollar and Federal Funds futures. </div><div style="margin-top:6pt;">The Fund may invest in short-term paper, cash and cash equivalents, including shares of affiliated and unaffiliated money market funds, in order to achieve its investment objective.</div><div style="margin-top:6pt;">The Fund may make the foregoing investments either directly or indirectly by investing in Underlying Funds, such as indexed or actively managed ETFs or other registered investment companies that invest in such securities. The Underlying Funds in which the Fund may invest include funds managed by NTI or its affiliates. </div><div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">The Fund is an actively managed ETF that does not seek to replicate the performance of a specified index. The Fund may have a higher degree of portfolio turnover than funds that seek to replicate the performance of an index. </div><div style="margin-top:6pt;">The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received).</div> Principal Risks <div style="margin-top:6pt;">Management Risk is the risk that a strategy used by NTI may fail to produce the intended results or that imperfections, errors or limitations in the tools and data used by NTI may cause unintended results.</div> <div style="margin-top:6pt;">Underlying Fund Risk is the risk that the Fund’s investment performance and its ability to achieve its investment objective may be directly related to the performance of the Underlying Funds in which it invests. There can be no assurance that the Underlying Funds will achieve their respective investment objectives. The Fund is subject to the risks of the Underlying Funds in direct proportion to the allocation of its assets among the Underlying Funds. By investing in the Underlying Funds indirectly through the Fund, you will incur not only a proportionate share of the expenses of the Underlying Fund held by the Fund (including operating costs and investment management fees), but also expenses of the Fund. NTI may be subject to potential conflicts of interest with respect to investments in affiliated Underlying Funds, which are Underlying Funds managed </div><div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">by NTI or its affiliates, because the fees paid to NTI by some affiliated Underlying Funds may be higher than the fees paid by other Underlying Funds.</div><div style="margin-top:6pt;">Sampling Risk is the risk that the index-based ETFs in which the Fund invests may utilize a representative sampling approach to track their respective underlying indices. ETFs that utilize a representative sampling approach are subject to an increased risk of tracking error because the securities selected for the ETF in the aggregate may vary from the investment profile of the underlying index. Additionally, if using a representative sampling approach, an ETF will typically hold a smaller number of securities than the underlying index, and as a result, an adverse development to an issuer of securities that the ETF holds could result in a greater decline in NAV than would be the case if the ETF held all of the securities in the underlying index.</div><div style="margin-top:6pt;">Tracking Risk is the risk that the index-based ETFs and other investment companies in which the Fund invests may not be able to replicate exactly the performance of the indices they track as a result of share purchases and redemptions, transaction costs, expenses and other factors. In addition, index-based ETFs and other investment companies in which the Fund invests may incur expenses not incurred by their applicable indices. Certain securities comprising the indices may, from time to time, temporarily be unavailable, which may further impede an ETF’s or other investment company’s ability to track its applicable index or match its performance.</div> <div style="margin-top:6pt;">Market Risk is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, changes in interest rates, lack of liquidity in the bond or equity markets, or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. Such events </div><div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">could result in the Fund’s shares trading at increased premiums or discounts to the Fund’s NAV. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to the risks described elsewhere in this summary will likely increase.</div> <div style="margin-top:6pt;">Income Risk is the risk that the Fund’s income may decline when interest rates fall. This decline can occur because the Fund must invest in lower-yielding bonds as bonds in its portfolio mature, bonds in an Underlying Fund’s underlying index are substituted or the Fund otherwise needs to purchase additional bonds.</div> <div style="margin-top:6pt;">Asset-Backed and Mortgage-Backed Securities Risk. Asset-backed and mortgage-backed securities may be less liquid than other bonds, and may be more sensitive than other bonds to the market’s perception of issuers and creditworthiness of payees, particularly in declining general economic conditions when concern regarding mortgagees’ ability to pay (e.g., the ability of homeowners, commercial mortgagees, consumers with student loans, automobile loans or credit card debtholders to make payments on the underlying loan pools) rises, which may result in the Fund experiencing difficulty selling or valuing these securities. In addition, these securities may not be backed by the full faith and credit of the U.S. government, have experienced extraordinary weakness and volatility at various times in recent years, and may decline quickly in the event of a substantial economic or market downturn. Those asset-backed and mortgage-backed securities that are guaranteed as to the timely payment of interest and principal by a government entity, are not guaranteed as to market price, which will fluctuate. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain asset-backed and mortgage-backed securities. </div> <div style="margin-top:6pt;">Authorized Participant Concentration Risk is the risk that the Fund may be adversely affected because it has a limited number of institutions that act as authorized participants (“Authorized Participants”). Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. To the extent that these institutions exit the business or are unable or unwilling to proceed with creation and/or redemption orders with respect to the </div><div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">Fund and no other Authorized Participant is able or willing to step forward to create or redeem Creation Units (as defined below), Fund shares may trade at a discount to NAV and possibly face trading halts and/or delisting.</div> <div style="margin-top:6pt;">Market Trading Risk is the risk that the Fund faces because its shares are listed on a securities exchange, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.</div><div style="margin-top:6pt;">Trading in Fund shares may be halted due to market conditions or for reasons that, in the view of its listing exchange, make trading in the shares inadvisable. The market price of Fund shares will generally fluctuate in accordance with changes in its NAV, changes in the relative supply of, and demand for, Fund shares, and changes in the liquidity or perceived liquidity, of the Fund’s holdings.</div> <div style="margin-top:6pt;">Credit (or Default) Risk is the risk that the inability or unwillingness of an issuer or guarantor of a fixed-income security, or a counterparty to a TBA, repurchase or other transaction, to meet its payment or other financial obligations will adversely affect the value of the Fund’s investments and its returns. The credit quality of a debt security or of the issuer of a debt security held by the Fund could deteriorate rapidly, which may impair the Fund's liquidity or cause a deterioration in the Fund's NAV. The Fund could also be delayed or hindered in its enforcement of rights against an issuer, guarantor or counterparty. The degree of credit risk depends on the issuer’s or counterparty’s financial condition and on the terms of the securities.</div> <div style="margin-top:6pt;">Debt Extension Risk is the risk that when interest rates rise an issuer will exercise its right to pay principal on certain debt securities held by the Fund later than expected. This will cause the value of the security, and the Fund’s NAV, to decrease, and the Fund may lose opportunities to invest in higher yielding securities.</div> <div style="margin-top:6pt;">Derivatives Risk is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the </div><div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.</div>•Futures Contracts Risk is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of NTI to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.•Swap Contracts Risk Swap contracts involve the risk that the counterparty with whom the Fund has entered into the agreement will default on its obligation to pay the Fund. While certain swaps are subject to mandatory central clearing, which is intended to reduce counterparty risk, these swaps are subject to the risk that a central clearinghouse will go into bankruptcy or become non-operational, and sometimes involve increased transaction costs. <div style="margin-top:6pt;">Sector Risk is the risk that companies in similar businesses may be similarly affected by particular economic or market events, which may, in certain circumstances, cause the value of securities of all companies in a particular sector of the market to decrease.</div> <div style="margin-top:6pt;">Hedging Risk is the risk that the Fund’s short positions in U.S. Treasury futures and transactions in interest rate swaps will not completely eliminate interest rate risk of long positions in bonds. The Fund seeks to mitigate the potential impact of interest rates on the performance of bonds by entering into short positions in U.S. Treasury futures or transact in interest rate swaps. The Fund’s short positions in U.S. Treasury futures and interest rate swaps are not intended to mitigate credit spread risk or other factors influencing the price of bonds, which may have a greater impact than interest rates. In addition, when interest rates fall, long-only bond investments will perform bet</div><div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">ter than the Fund’s investments. In certain falling interest rate environments, the Fund’s hedging strategy could result in disproportionately larger losses in the short U.S. Treasury futures and interest rate swaps positions as compared to gains in the long bond positions attributable to interest rate changes. There is no guarantee the Fund will have positive returns, even in environments of sharply rising Treasury interest rates in which the Fund’s short positions might be expected to mitigate the effects of such rises. The Fund will incur expenses when entering into short positions.</div> <div style="margin-top:6pt;">High Portfolio Turnover Risk is the risk that active and frequent trading of the Fund’s portfolio securities may result in increased transaction costs to the Fund, including brokerage commissions, dealer mark-ups and other transaction costs, which could reduce the Fund’s return. </div> <div style="margin-top:6pt;">Interest Rate/Maturity Risk is the risk that the value of the Fund’s fixed-income assets will decline because of rising interest rates. In general, securities with longer maturities or durations are more sensitive to interest rate changes. Changing interest rates, including rates that fall below zero, may have unpredictable effects on the markets and the Fund’s investments, may result in heightened market volatility, may impact the liquidity of fixed-income securities and of the Fund, and may detract from Fund performance. A low or negative interest rate environment could cause the Fund’s earnings to fall below the Fund’s expense ratio, resulting in a negative yield and a decline in the Fund’s share price. An increase in interest rates may cause investors to move out of fixed income securities on a large scale, which could adversely affect the price of fixed income securities, lead to heightened volatility in the fixed-income markets and may adversely affect the liquidity of certain fixed-income investments. During periods when inflation rates are high or rising, or during periods of low interest rates, the Fund may be subject to a greater risk of rising interest rates.</div> <div style="margin-top:6pt;">Leveraging Risk is the risk that certain transactions of the Fund, such as the use of when-issued, delayed delivery or forward commitment transactions and investments in forward foreign currency contracts, may give rise to leverage, causing the Fund to be more volatile than if it had not been leveraged.</div> <div style="margin-top:6pt;">Liquidity Risk is the risk that certain portfolio securities may be less liquid or may become less liquid than others, which may make them difficult or impossible to sell at the </div><div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">time and the price that the Fund would like, adversely affecting the value of the Fund’s investments and its returns. Illiquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. Liquidity risk may result from the lack of an active market, reduced number and capacity of traditional market participants to make a market in fixed income securities, and may be magnified in a rising interest rate environment or other circumstances where investor redemptions from fixed income funds may be higher than normal, causing increased supply in the market due to selling activity. The market for certain investments may become illiquid under adverse market or economic conditions independent of any specific adverse changes in the conditions of a particular issuer. Additionally, in adverse market conditions, the Fund’s market price may begin to reflect illiquidity or pricing uncertainty of the Fund’s portfolio securities. This could lead to the Fund’s shares trading at a price that is higher or lower than the Fund’s NAV. At times, such differences may be significant.</div> <div style="margin-top:6pt;">Foreign Securities Risk is the risk that investing in foreign (non-U.S.) securities may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies, due to less liquid markets and adverse economic, political, diplomatic, financial, and regulatory factors. Foreign governments may impose limitations on foreigners’ ownership of interests in local issuers, restrictions on the ability to repatriate assets, and may also impose taxes. Any of these events could cause the value of the Fund’s investments to decline. Foreign banks, agents and securities depositories that hold the Fund’s foreign assets may be subject to little or no regulatory oversight over, or independent evaluation, of their operations. Additional costs associated with investments in foreign securities may include higher custodial fees than those applicable to domestic custodial arrangements and transaction costs of foreign currency conversions. Unless the Fund has hedged its foreign currency exposure, foreign securities risk also involves the risk of negative foreign currency rate fluctuations, which may cause the value of securities denominated in such foreign currency (or other instruments through which the Fund has exposure to foreign currencies) to decline in value. Currency exchange rates may fluctuate significantly over </div><div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">short periods of time. Currency hedging strategies, if used, are not always successful. For instance, forward foreign currency exchange contracts, if used by the Fund, could reduce performance if there are unanticipated changes in currency exchange rates.</div> <div style="margin-top:6pt;">Geographic Risk is the risk that if the Fund invests a significant portion of its total assets in certain issuers within the same country or geographic region, an adverse economic, business or political development affecting that country or region may affect the value of the Fund’s investments more, and the Fund's investments may be more volatile than if the Fund’s investments were not so concentrated in such country or region.</div> <div style="margin-top:6pt;">Prepayment (or Call) Risk is the risk that an issuer could exercise its right to pay principal on callable debt securities held by the Fund earlier than expected. Issuers may be more likely to prepay when interest rates fall, when credit spreads change, or when an issuer’s credit quality improves. If this happens, the Fund will not benefit from the rise in the market price of the securities that normally accompanies a decline in interest rates, and will be forced to reinvest prepayment proceeds in lower yielding securities, which may reduce the Fund’s returns. The Fund may also lose any premium it paid to purchase the securities.</div> <div style="margin-top:6pt;">TBA Transactions Risk is the risk of loss if the securities received are less favorable than what was anticipated by the Fund when entering into the TBA transaction. TBA transactions also involve the risk that the counterparty will fail to deliver the securities, exposing the Fund to further losses. Default or bankruptcy of a counterparty to a TBA transaction would expose the Fund to possible losses because of adverse market action, expenses or delays in connection with the purchase or sale of the pools of mortgage pass-through securities specified in the TBA transaction. Whether or not the Fund takes delivery of the securities at the termination date of a TBA transaction, the Fund will nonetheless be exposed to changes in the value of the underlying investments during the term of the agreement.</div> <div style="margin-top:6pt;">Securities Lending Risk is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral. </div> <div style="line-height:13.10pt;margin-top:0.00pt;text-align:left;">U.S. Government Securities Risk is the risk that the U.S. government will not provide financial support to its agencies, instrumentalities or sponsored enterprises if it is not obligated to do so by law. Many U.S. government securities that may be purchased by the Fund are not backed by the full faith and credit of the United States. The maximum potential liability of the issuers of some U.S. government securities may greatly exceed their current resources, including any legal right to support from the U.S. Treasury. It is possible that the issuers of such securities will not have the funds to meet their payment obligations in the future.</div> It is possible to lose money on an investment in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank. Fund Performance <div style="margin-top:6pt;">The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year and (B) how the Fund’s average annual returns compare with those of a broad measure of market performance. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated information on the Fund’s performance results can be obtained by visiting flexshares.com.</div> The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund by showing (A) changes in the Fund’s performance from year to year and (B) how the Fund’s average annual returns compare with those of a broad measure of market performance. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. flexshares.com Calendar Year Total Returns <div style="margin-top:6pt;">For the periods in the bar chart above:</div><div style="margin-top:6pt;">Best Quarter (12/31/2023): 6.89%</div><div style="margin-top:6pt;">Worst Quarter (3/31/2022): -6.21%</div> Best Quarter 2023-12-31 0.0689 Worst Quarter 2022-03-31 -0.0621 Average Annual Total Returns(for the periods ended December 31, 2024) 0.0093 -0.0038 0.0110 2016-11-18 -0.0059 -0.0150 -0.0006 0.0055 -0.0074 0.0035 0.0125 -0.0033 0.0128 Reflects no deduction for fees, expenses or taxes. <div style="margin-top:6pt;">After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares.</div> After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. After-tax returns shown are not relevant to investors who hold shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement plans. After-tax returns may exceed the return before taxes due to an assumed tax benefit from realizing a capital loss on a sale of Fund shares. “Management Fees” have been restated to reflect current fees. In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the Morningstar® U.S. Market Factor Tilt IndexSM to the Russell 3000 Index. The Fund will continue to compare its performance to the Morningstar® U.S. Market Factor Tilt IndexSM, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.39%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the Morningstar® Developed Markets ex-US Factor Tilt IndexSM to the MSCI World ex-USA Index. The Fund will continue to compare its performance to the Morningstar® Developed Markets ex-US Factor Tilt IndexSM, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.57%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the Morningstar® Emerging Markets Factor Tilt IndexSM to the MSCI Emerging Markets Index. The Fund will continue to compare its performance to the Morningstar® Emerging Markets Factor Tilt IndexSM, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.25%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. Reflects no deduction for fees, expenses or taxes. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.32%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. Reflects no deduction for fees, expenses or taxes. Formerly known as STOXX® USA ESG Impact IndexSM. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.42%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. Reflects no deduction for fees, expenses or taxes. Formerly known as STOXX® Global ESG Impact IndexSM. Reflects no deduction for fees, expenses or taxes. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.09%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the S&P 500 Index to the Russell 1000® Index. The Fund will continue to compare its performance to the S&P 500 Index, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.12%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. Reflects no deduction for fees, expenses or taxes. “Management Fees” have been restated to reflect current fees. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.46%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the Morningstar® Global Upstream Natural Resources IndexSM to the MSCI ACWI Index. The Fund will continue to compare its performance to the Morningstar® Global Upstream Natural Resources IndexSM, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.47%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.12%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the STOXX® Global Broad Infrastructure Index to the MSCI ACWI Index. The Fund will continue to compare its performance to the STOXX® Global Broad Infrastructure Index, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.45%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the FTSE EPRA/NAREIT Developed IndexSM to the MSCI World Index. The Fund will continue to compare its performance to the FTSE EPRA/NAREIT Developed IndexSM, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. The “Total Annual Fund Operating Expenses” may not correlate to the ratio of expenses to average net assets as reported in the "Financial Highlights" section of the Prospectus, which reflects the operating expenses of the Fund and does not include “Acquired Fund Fees and Expenses.” Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses (“Acquired Fund Fees and Expenses”)) to the extent the “Total Annual Fund Operating Expenses” exceed 0.49%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. NTI also has contractually agreed until March 1, 2026 to waive a portion of its Management Fees and/or reimburse certain operating expenses in an amount equal to the Acquired Fund Fees and Expenses attributable to the Fund’s investments in the Underlying Fund (as defined below). The Fund’s Board of Trustees may terminate the contractual agreements at any time if it determines that it is in the best interest of the Fund and its shareholders. Reflects no deduction for fees, expenses or taxes. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.37%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. Reflects no deduction for fees, expenses or taxes. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.37%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. Reflects no deduction for fees, expenses or taxes. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.47%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. Reflects no deduction for fees, expenses or taxes. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.08%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.47%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. Reflects no deduction for fees, expenses or taxes. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.18%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. Reflects no deduction for fees, expenses or taxes. In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the iBoxx 3-Year Target Duration TIPS Index to the Bloomberg U.S. Aggregate Bond Index. The Fund will continue to compare its performance to the iBoxx 3-Year Target Duration TIPS Index, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.18%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the iBoxx 5-Year Target Duration TIPS Index to the Bloomberg U.S. Aggregate Bond Index. The Fund will continue to compare its performance to the iBoxx 5-Year Target Duration TIPS Index, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.20%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the ICE BofA® Constrained Duration US Mortgage Backed Securities IndexSM to the Bloomberg U.S. Aggregate Bond Index. The Fund will continue to compare its performance to the ICE BofA® Constrained Duration US Mortgage Backed Securities IndexSM, which reflects the market segments in which the Fund invests. Prior to July 1, 2022, index returns reflect no deduction for fees, expenses or taxes. Effective July 1, 2022, index returns reflect no deduction for taxes, but include transaction costs, which may be higher or lower than the actual transaction costs incurred by the Fund. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.15%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. Reflects no deduction for fees, expenses or taxes. In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the Bloomberg U.S. Intermediate Corporate Bond Index to the Bloomberg U.S. Aggregate Bond Index. The Fund will continue to compare its performance to the Bloomberg U.S. Intermediate Corporate Bond Index, which reflects the market segments in which the Fund invests. “Management Fees” have been restated to reflect current fees. The hybrid index performance information reflects the performance of the Northern Trust Credit-Scored US Corporate Bond IndexSM (Previous Index) through April 30, 2020 and the Northern Trust US Corporate Bond Quality Value IndexSM thereafter. The Previous Index terminated as of May 1, 2020. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.15%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the Bloomberg Long U.S. Corporate Bond Index to the Bloomberg U.S. Aggregate Bond Index. The Fund will continue to compare its performance to the Bloomberg Long U.S. Corporate Bond Index, which reflects the market segments in which the Fund invests. Reflects no deduction for fees, expenses or taxes. The hybrid index performance information reflects the performance of the Northern Trust Credit-Scored US Long Corporate Bond IndexSM (Previous Index) through April 30, 2020 and the Northern Trust US Long Corporate Bond Quality Value IndexSM thereafter. The Previous Index terminated as of May 1, 2020. Northern Trust Investments, Inc. (“NTI”) has contractually agreed to reimburse a portion of the operating expenses of the Fund (other than 12b-1 Fees, Tax Expenses, Extraordinary Expenses, and Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.37%. This contractual limitation may not be terminated before March 1, 2026 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders. In connection with new regulatory requirements, the Fund has changed its broad-based securities market benchmark from the ICE BofA® US High Yield Index to the Bloomberg Universal Index. The Fund will continue to compare its performance to the ICE BofA® US High Yield Index, which reflects the market segments in which the Fund invests. Prior to July 1, 2022, index returns reflect no deduction for fees, expenses or taxes. Effective July 1, 2022, index returns reflect no deduction for taxes, but include transaction costs, which may be higher or lower than the actual transaction costs incurred by the Fund.