Summary Prospectus by Investment Company - Form 497K

Portfolio Turnover. The Fund may pay 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 the Annual Fund Operating Expenses or in the Example, affect the Fund's performance. There has been no portfolio turnover because the Fund has not commenced operations as of the date of this prospectus (the "Prospectus").

Principal Investment Strategies

The Fund typically invests more than 90% of its assets in a diversified portfolio of fixed-income securities such as corporate bonds and notes, mortgage-backed securities, asset-backed securities, convertible securities, preferred securities and government obligations. Both U.S. and foreign companies and governments may issue these securities. Under normal circumstances, the Fund invests primarily in fixed-income securities. The Fund may invest in fixed-income securities of any duration or maturity.

The Fund may invest up to 30% of its net assets in securities of foreign

issuers, of which 20% (as a percentage of the Fund's net assets) may be in emerging markets issuers. Investments in U.S. dollar-denominated securities of foreign issuers, excluding issuers from emerging markets, are permitted beyond the 30% limit. This means that the Fund may invest in such U.S. dollar-denominated securities of foreign issuers without limit. The Fund may also invest in derivative securities for hedging purposes or to increase the return on its investments. The Fund may also invest in credit-linked notes, credit-linked trust certificates, structured notes, or other instruments evidencing interests in special purpose vehicles, trusts, or other entities that hold or represent interests in fixed-income securities. The Fund may also enter into reverse repurchase agreements and mortgage dollar rolls.

The Fund may invest up to 20% of its net assets in fixed-income securities that are rated below investment grade by the Nationally Recognized Statistical Rating Organizations ("NRSROs"), including Moody's Investor Service, Inc. ("Moody's"), S&P Global Ratings ("S&P") or Fitch Ratings, Inc. ("Fitch"), or in unrated securities of equivalent credit quality. Split rated bonds will be considered to have the higher credit rating.

The Fund may invest up to 15% of its net assets in collateralized debt

obligations ("CDOs"), of which 10% (as a percentage of the Fund's net assets) may be in collateralized loan obligations ("CLOs"). CDOs are types of asset-backed securities. CLOs are ordinarily issued by a trust or other special purpose entity and are typically collateralized by a pool of loans, which may include, among others, domestic and non-U.S. senior secured loans, senior unsecured loans, and subordinate corporate loans, including loans that may be rated below investment grade or equivalent unrated loans, held by such issuer.

The Fund may seek to provide exposure to the investment returns of real assets that trade in the commodity markets through investment in commodity-linked derivative instruments and investment vehicles that exclusively invest in commodities such as exchange-traded funds ("ETFs"), which are designed to provide this exposure without direct investment in physical commodities. The Fund may also gain exposure to commodity markets by investing up to 25% of its total assets in BlackRock Cayman Total Return ETF, Ltd. (the "Subsidiary"), a wholly owned subsidiary of the Fund formed in the Cayman Islands, which invests primarily in commodity-related instruments.

The Fund may engage in active and frequent trading of portfolio securities to achieve its primary investment strategies.

Summary of Principal Risks

As with any investment, you could lose all or part of your investment in the Fund, and the Fund's performance could trail that of other investments. The Fund is subject to certain risks, including the principal risks noted

below, any of which may adversely affect the Fund's net asset value per share ("NAV"), trading price, yield, total return and ability to meet its investment objective. Unlike many ETFs, the Fund is not an index-based ETF. Certain key risks are prioritized below (with others following in alphabetical order), but the relative significance of any risk is difficult to predict and may change over time. You should review each risk factor carefully.

Interest Rate Risk. During periods of very low or negative interest rates, the Fund may be unable to maintain positive returns or pay dividends to Fund shareholders. Very low or negative interest rates may magnify interest rate risk. Changing interest rates, including rates that fall below zero, may have unpredictable effects on markets, result in heightened market volatility and detract from the Fund's performance to the extent the Fund is exposed to such interest rates. Additionally, under certain market conditions in which interest rates are low and the market prices for portfolio securities have increased, the Fund may have a very low or even negative yield. A low or negative yield would cause the Fund to lose money in certain conditions and over certain time periods. An increase in interest rates will generally cause the value of securities held by the Fund to decline, may lead to heightened volatility in the fixed-income markets and may adversely affect the liquidity of certain fixed-income investments, including those held by the Fund. Because rates on certain floating rate debt securities typically reset only periodically, changes in prevailing interest rates (and particularly sudden and significant changes) can be expected to cause

some fluctuations in the net asset value of the Fund to the extent that it invests in floating rate debt securities. The historically low interest rate environment in recent years heightens the risks associated with rising interest rates.

Income Risk. Income risk is the risk that the Fund's yield will vary as short-term securities in its portfolio mature and the proceeds are reinvested in securities with different interest rates.

Credit Risk. Debt issuers and other counterparties may be unable or unwilling to make timely interest and/or principal payments when due or otherwise honor their obligations. Changes in an issuer's credit rating or the market's perception of an issuer's creditworthiness may also adversely affect the value of the Fund's investment in that issuer. The degree of credit risk depends on an issuer's or counterparty's financial condition and on the terms of an obligation.

Call Risk. During periods of falling interest rates, an issuer of a callable bond held by the Fund may "call" or repay the security before its stated maturity, and the Fund may have to reinvest the proceeds in securities with lower yields, which would result in a decline in the Fund's income, or in securities with greater risks or with other less favorable features.

Extension Risk. During periods of rising interest rates, certain debt obligations may be paid off substantially more slowly than originally anticipated and the value of those securities may fall sharply, resulting in a decline in the Fund's income and potentially in the value of the Fund's investments.

Prepayment Risk. During periods of falling interest rates, issuers of certain debt obligations may repay principal prior to the security's maturity, which may cause the Fund to have to reinvest in securities with lower yields or higher risk of default, resulting in a decline in the Fund's income or return potential.

Asset-Backed and Mortgage-Backed Securities Risk. Asset-backed securities ("ABS") and mortgage-backed securities ("MBS") (residential and commercial) represent interests in "pools" of mortgages or other assets, including consumer loans or receivables held in trust. ABS and MBS are subject to credit, interest rate, call, extension, valuation and liquidity risk. These securities, in most cases, are not backed by the full faith and credit of the U.S. government and are subject to the risk of default on the underlying asset or mortgage, particularly during periods of economic downturn. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain ABS and MBS.

U.S. Government Issuers Risk. Treasury obligations may differ in their interest rates, maturities, times of issuance and other characteristics. Obligations of U.S. government agencies and authorities are supported by varying degrees of credit, but generally are not backed by the full faith and credit of the U.S. government. Similar to other issuers, changes to the financial condition or credit rating of the U.S. government or U.S. government agencies and authorities may cause the value of the Fund's investments to decline.

Asset Class Risk. Securities and other assets in the Fund's portfolio may

underperform in comparison to the general financial markets, a particular financial market or other asset classes.

Authorized Participant Concentration Risk. Only an Authorized Participant (as defined in the Creations and Redemptions section of this Prospectus) 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. The Fund has a limited number of institutions that may act as Authorized Participants on an agency basis (i.e., on behalf of other market participants). To the extent that Authorized Participants exit the business or are unable to proceed with creation or redemption orders with respect to the Fund and no other Authorized Participant is able to step forward to create or redeem, Fund shares may be more likely to trade at a premium or discount to NAV and possibly face trading halts or delisting.

Cash Management Risk. If a significant amount of the Fund's assets is invested in cash and cash equivalents, the Fund may underperform other funds that do not similarly invest in cash and cash equivalents for investment purposes and/or to collateralize derivative instruments.

Cash Transactions Risk. The Fund expects to effect all of its creations and redemptions for cash, rather than in-kind securities. As a result, 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 and recognize a capital gain or loss that might not have been

incurred if it had made a redemption in-kind. The use of cash creations and redemptions may also cause the Fund's shares to trade in the market at wider bid-ask spreads or greater premiums or discounts to the Fund's NAV.

Collateralized Debt Obligations Risk. In addition to the typical risks associated with fixed-income securities and asset-backed securities, CDOs, including CLOs, carry additional risks including, but not limited to: (i) the possibility that distributions from collateral securities will not be adequate to make interest or other payments; (ii) the risk that the collateral may default or decline in value or be downgraded, if rated by a nationally recognized statistical rating organization; (iii) the Fund may invest in tranches of CDOs that are subordinate to other tranches; (iv) the structure and complexity of the transaction and the legal documents could lead to disputes among investors regarding the characterization of proceeds; (v) the investment return achieved by the Fund could be significantly different than those predicted by financial models; (vi) the lack of a readily available secondary market for CDOs; (vii) the risk of forced "fire sale" liquidation due to technical defaults such as coverage test failures; and (viii) the CDO's manager may perform poorly.

Commodities Related Investments Risk. Exposure to the commodities markets may subject the Fund to greater volatility than investments in traditional securities. The value of commodity-linked derivative investments may be affected by changes in overall market movements, commodity index volatility, changes in interest rates, or factors affecting a

particular industry or commodity, such as drought, floods, weather, embargoes, tariffs and international economic, political and regulatory developments.

Convertible Securities Risk. The market price of a convertible security generally tends to behave like that of a regular debt security; that is, if market interest rates rise, the value of a convertible security usually falls. In addition, convertible securities are subject to the risk that the issuer will not be able to pay interest, principal or dividends when due, and their market value may change based on changes in the issuer's credit rating or the market's perception of the issuer's creditworthiness. Because a convertible security derives a portion of its value from the common stock into which it may be converted, a convertible security is also subject to the same types of market and issuer risks that apply to the underlying common stock, including the potential for increased volatility in the price of the convertible security.

Cybersecurity Risk. Failures or breaches of the electronic systems of the Fund, the Fund's adviser, distributor, service providers, or the issuers of securities in which the Fund invests have the ability to cause disruptions, negatively impact the Fund's business operations and/or potentially result in financial losses to the Fund and its shareholders. While the Fund has established business continuity plans and risk management systems seeking to address system breaches or failures, there are inherent limitations in such plans and systems. Furthermore, the Fund cannot control the cybersecurity plans and systems of the Fund's service providers or issuers of securities in which the Fund invests.

Derivatives Risk. The Fund's use of derivatives, including commodity-related futures, options on futures and swaps, may reduce the Fund's returns or increase volatility. Volatility is defined as the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. Derivatives may also be subject to counterparty risk, which is the risk that the other party in the transaction will not fulfill its contractual obligation. A risk of the Fund's use of derivatives is that the fluctuations in their values may not correlate perfectly with the value of the underlying asset, the performance of the asset class to which the Fund seeks exposure or to the performance of the overall securities markets. The possible lack of a liquid secondary market for derivatives and the resulting inability of the Fund to sell or otherwise close a derivatives position could expose the Fund to losses and could make derivatives more difficult for the Fund to value accurately. The Fund could also suffer losses related to its derivatives positions as a result of unanticipated market movements, which losses are potentially unlimited. Certain derivatives may give rise to a form of leverage and may expose the Fund to greater risk and increase its costs. To the extent that the Fund invests in rolling futures contracts, it may be subject to additional risk. The impact of U.S. and global regulation of derivatives may make derivatives more costly, may limit the availability of derivatives, may delay or restrict the exercise by the Fund of termination rights or remedies upon a counterparty default under derivatives held by the Fund (which could result in losses), or may otherwise adversely affect the

value or performance of derivatives. In addition, the Fund's use of derivatives may expose the Fund to risks related to potential operational issues, such as documentation and settlement issues, systems failures, inadequate controls and human error. Derivatives may also involve legal risks, including insufficient documentation, insufficient capacity or authority of a counterparty, and legality and enforceability of a contract.

Dollar Rolls Risk. Dollar rolls involve the risk that the market value of the securities that the Fund is committed to buy may decline below the price of the securities the Fund has sold. These transactions may involve leverage.

High Portfolio Turnover Risk. The Fund may engage in active and frequent trading of its portfolio securities. High portfolio turnover (considered by the Fund to mean higher than 100% annually) may result in increased transaction costs to the Fund, including brokerage commissions, dealer mark-ups and other transaction costs on the sale of the securities and on reinvestment in other securities.

High Yield Securities Risk. Securities that are rated below investment-grade (commonly referred to as "junk bonds," which may include those bonds rated below "BBB-" by S&P and Fitch or below "Baa3" by Moody's), or are unrated, may be deemed speculative, may involve greater levels of risk than higher-rated securities of similar maturity and may be more likely to default.

Infectious Illness Risk. A widespread outbreak of an infectious illness, such as the COVID-19 pandemic, may result in travel restrictions, disruption of healthcare services, prolonged

quarantines, cancellations, supply chain disruptions, business closures, lower consumer demand, layoffs, ratings downgrades, defaults and other significant economic, social and political impacts. Markets may experience temporary closures, extreme volatility, severe losses, reduced liquidity and increased trading costs. Such events may adversely affect the Fund and its investments and may impact the Fund's ability to purchase or sell securities or cause increased premiums or discounts to the Fund's NAV. Despite the development of vaccines, the duration of the COVID-19 pandemic and its effects cannot be predicted with certainty.

Large Shareholder and Large-Scale Redemption Risk. Certain shareholders, including an Authorized Participant, a third-party investor, the Fund's adviser or an affiliate of the Fund's adviser, a market maker, or another entity, may from time to time own or manage a substantial amount of Fund shares, or may invest in the Fund and hold their investment for a limited period of time. There can be no assurance that any large shareholder or large group of shareholders would not redeem their investment. Redemptions of a large number of Fund shares could require the Fund to dispose of assets to meet the redemption requests, which can accelerate the realization of taxable income and/or capital gains and cause the Fund to make taxable distributions to its shareholders earlier than the Fund otherwise would have. In addition, under certain circumstances, non-redeeming shareholders may be treated as receiving a disproportionately large taxable distribution during or with respect to such year. In some circumstances, the

Fund may hold a relatively large proportion of its assets in cash in anticipation of large redemptions, diluting its investment returns. These large redemptions may also force the Fund to sell portfolio securities when it might not otherwise do so, which may negatively impact the Fund's NAV, increase the Fund's brokerage costs and/or have a material effect on the market price of the Fund shares.

Leverage Risk. Some transactions may give rise to a form of economic leverage. These transactions may include, among others, derivatives, and may expose the Fund to greater risk and increase its costs. The use of leverage may cause the Fund to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet the applicable requirements of the Investment Company Act of 1940, as amended (the "Investment Company Act"), and the rules thereunder. Increases and decreases in the value of the Fund's portfolio will be magnified when the Fund uses leverage.

Management Risk. The Fund is subject to management risk, which is the risk that the investment process, techniques and analyses applied by BFA will not produce the desired results, and those securities or other financial instruments selected by BFA may result in returns that are inconsistent with the Fund's investment objective. In addition, legislative, regulatory, or tax developments may affect the investment techniques available to BFA in connection with managing the Fund and may also adversely affect the ability of the Fund to achieve its investment objective.

Market Risk. The Fund could lose money over short periods due to short-term market movements and over longer periods during more prolonged market downturns. Local, regional or global events such as war, acts of terrorism, the spread of infectious illness or other public health issues, recessions, or other events could have a significant impact on the Fund and its investments and could result in increased premiums or discounts to the Fund's NAV.

Market Trading Risk. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruptions in the creation/redemption process. Unlike some ETFs that track specific indexes, the Fund does not seek to replicate the performance of a specified index. Index-based ETFs have generally traded at prices that closely correspond to NAV per share. Given the high level of transparency of the Fund's holdings, BFA believes that the trading experience of the Fund should be similar to that of index-based ETFs. However, ETFs that do not seek to replicate the performance of a specified index have a limited trading history and, therefore, there can be no assurance as to whether, and/or the extent to which, the Fund's shares will trade at premiums or discounts to NAV. ANY OF THESE FACTORS, AMONG OTHERS, MAY LEAD TO THE FUND'S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Non-U.S. Issuers Risk. Securities issued by non-U.S. issuers carry different risks from securities issued by U.S. issuers. These risks include

differences in accounting, auditing and financial reporting standards, the possibility of expropriation or confiscatory taxation, adverse changes in investment or exchange control regulations, political instability, regulatory and economic differences, and potential restrictions on the flow of international capital.

Preferred Securities Risk. Preferred securities may pay fixed or adjustable rates of return. Preferred securities are subject to issuer-specific and market risks applicable generally to equity securities. In addition, a company's preferred securities generally pay dividends only after the company makes required payments to holders of its bonds and other debt. For this reason, the value of preferred securities will usually react more strongly than bonds and other debt to actual or perceived changes in the company's financial condition or prospects. Preferred securities of smaller companies may be more vulnerable to adverse developments than preferred securities of larger companies.

Risk of Investing in Emerging Markets. Investments in emerging market issuers may be subject to a greater risk of loss than investments in issuers located or operating in more developed markets. Emerging markets may be more likely to experience inflation, social instability, political turmoil or rapid changes in economic conditions than more developed markets. Companies in many emerging markets are not subject to the same degree of regulatory requirements, accounting standards or auditor oversight as companies in more developed countries, and as a result, information about the securities in which the Fund invests may be less

reliable or complete. Emerging markets often have less reliable securities valuations and greater risk associated with custody of securities than developed markets. There may be significant obstacles to obtaining information necessary for investigations into or litigation against companies and shareholders may have limited legal remedies.

Reverse Repurchase Agreements Risk. Reverse repurchase agreements involve the sale of securities held by the Fund with an agreement to repurchase the securities at an agreed-upon price, date and interest payment. Reverse repurchase agreements involve the risk that the other party may fail to return the securities in a timely manner or at all. The Fund could lose money if it is unable to recover the securities and the value of the collateral held by the Fund, including the value of the investments made with cash collateral, is less than the value of the securities. These events could also trigger adverse tax consequences for the Fund. In addition, reverse repurchase agreements involve the risk that the interest income earned in the investment of the proceeds will be less than the interest expense.

Risk of Investing in the U.S. Certain changes in the U.S. economy, such as when the U.S. economy weakens or when its financial markets decline, may have an adverse effect on the securities to which the Fund has exposure.

Sovereign Debt Risk. Sovereign debt instruments are subject to the risk that a governmental entity may delay or refuse to pay interest or repay principal on its sovereign debt, due, for example, to cash flow problems, insufficient foreign currency reserves, political considerations, the relative size of the

governmental entity's debt position in relation to the economy or the failure to put in place economic reforms required by the International Monetary Fund or other multilateral agencies.

Structured Notes Risk. Structured notes and other related instruments purchased by the Fund are generally privately negotiated debt obligations where the principal and/or interest is determined by reference to the performance of a specific asset, benchmark asset, market or interest rate ("reference measure"). The purchase of structured notes exposes the Fund to the credit risk of the issuer of the structured product. Structured notes may be leveraged, increasing the volatility of each structured note's value relative to the change in the reference measure. Structured notes may also be less liquid and more difficult to price accurately than less complex securities and instruments or more traditional debt securities.

Subsidiary Risk. By investing in the Subsidiary, the Fund is indirectly exposed to the risks associated with the Subsidiary's investments. The commodity-related instruments that may be held by the Subsidiary are generally similar to those that are permitted to be held by the Fund and are subject to the same risks that would apply to similar investments if held directly by the Fund. There can be no assurance that the investment objective of the Subsidiary will be achieved. The Subsidiary is not registered under the Investment Company Act, and, unless otherwise noted in this Prospectus, is not subject to the investor protections of the Investment Company Act. Changes in the laws of the U.S. and/or the Cayman

Islands could result in the inability of the Fund and/or the Subsidiary to operate as described in the Prospectus and the Statement of Additional Information ("SAI"), and could adversely affect the Fund.

Performance Information

Because the Fund has not commenced operations as of the date of this Prospectus, it does not have performance information an investor would find useful in evaluating the risks of investing in the Fund. The Fund's benchmark is the Bloomberg U.S. Aggregate Bond Index.

Management

Investment Adviser and Sub-Advisers.The Fund's investment adviser is BlackRock Fund Advisors. The Fund's sub-advisers are BlackRock International Limited ("BIL") and BlackRock (Singapore) Limited ("BSL" and together with BIL, the "Sub-Advisers"). Where applicable, the use of the term BFA also refers to the Fund's sub-advisers.

Portfolio Managers. Rick Rieder, David Rogal and Chi Chen (the "Portfolio Managers") are jointly and primarily responsible for the day-to-day management of the Fund. Mr. Rieder, Mr. Rogal and Ms. Chen have been Portfolio Managers of the Fund since 2023.

Purchase and Sale of Fund Shares

The Fund is an ETF. Individual shares of the Fund may only be bought and sold in the secondary market through a broker-dealer. Because ETF shares

trade at market prices rather than at NAV, shares may trade at a price greater than NAV (a premium) or less than NAV (a discount). An investor may incur costs attributable to the difference between the highest price a buyer is willing to pay to purchase shares of the Fund (bid) and the lowest price a seller is willing to accept for shares of the Fund (ask) when buying or selling shares in the secondary market (the "bid-ask spread").

Tax Information

The Fund intends to make distributions that may be taxable to your as ordinary income or capital gains, unless you are investing through a tax-deferred arrangement such as a 401(k) plan or an individual retirement account ("IRA"), in which case, your distributions generally will be taxable when withdrawn.

Payments to Broker-Dealers and Other Financial Intermediaries

If you purchase shares of the Fund through a broker-dealer or other financial intermediary (such as a bank), BFA or other related companies may pay the intermediary for marketing activities and presentations, educational training programs, conferences, the development of technology platforms and reporting systems or other services related to the sale or promotion of the Fund. These payments may create a conflict of interest by influencing the broker-dealer or other intermediary and your salesperson to recommend the Fund over another investment. Ask your salesperson or visit your financial intermediary's website for more information.