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. For the fiscal year ended July 31, 2025, the Fund's portfolio turnover rate was 89% of the average value of the portfolio.

Principal Investment Strategies

The Fund seeks to achieve its investment objective by investing, under normal circumstances, at least 80% of its assets in U.S. dollar-denominated CLOs that are, at the time of purchase, rated AAA (or equivalent) by at least one of the major rating agencies or, if unrated, determined by the Fund management team to be of similar quality. The Fund's investments in derivatives will be counted toward the Fund's 80% policy to the extent that they provide investment exposure to

the securities included within that policy or to one or more market risk factors associated with such securities. The Fund's 80% investment policy is non-fundamental and may be changed without shareholder approval upon 60 days' prior written notice to shareholders. The Fund may invest in CLOs of any maturity. The Fund may purchase CLOs in both the primary market (i.e., directly from arranging banks) and in the secondary market.

A CLO is ordinarily issued by a trust or other special purpose entity ("SPE") and is typically collateralized by a pool of loans, which may include, among others, domestic and non-U.S. senior secured loans, senior unsecured loans, "covenant lite" loans (which have few or no financial maintenance covenants) and subordinate corporate loans, including loans that may be rated below investment grade or equivalent unrated loans, and to a lesser extent, high yield bonds rated below investment grade (commonly called "junk bonds"), held by such issuer. The cash flows from the SPE are split into two or more portions, called tranches, varying in risk and yield. The riskiest portion of a CLO is the "equity" tranche, which bears the

first loss from defaults from the bonds or loans in the SPE and serves to protect the other, more senior tranches from default (though such protection is not complete). Since it is partially protected from defaults, a "senior" tranche of a CLO typically has higher ratings and lower yields than its underlying securities, and may be rated AAA.

The Fund may invest up to 20% of its assets in U.S. dollar-denominated CLOs that are, at the time of purchase, rated AA or A (or equivalent) by at least one of the major rating agencies or, if unrated, determined by the Fund management team to be of similar quality.

The Fund will not invest more than 10% of its net assets in any single CLO.

The Fund may invest in floating- and fixed-rate CLOs, but will not invest more than 10% of its net assets in fixed-rate CLOs.

The Fund may also buy when-issued securities and participate in delayed delivery transactions.

The Fund is classified as non-diversified under the Investment Company Act of 1940, as amended (the "Investment Company Act").

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 exchange-traded funds ("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 each risk factor below is difficult to predict and may change over time. You should review each risk factor carefully.

Collateralized Loan Obligations Risk. The risks of investing in CLOs depend largely on the type of the collateral securities and the tranche of the CLO. In stressed market conditions, it is possible that even senior CLO debt tranches, such as those in which the Fund will invest, could experience losses due to actual defaults, downgrades of the underlying collateral by rating agencies, forced liquidation of the collateral pool due to a failure of coverage tests, increased sensitivity to defaults due to collateral default and the disappearance of protecting tranches, market anticipation of defaults as well as investor aversion to CLO securities as an asset class. While the Fund invests principally in CLO tranches that are rated AAA, such ratings do not constitute a guarantee of credit quality and may be downgraded. To the extent that the Fund invests in CLO tranches rated below AAA, the risks of investing in CLOs will be greater. Split rated CLOs, which are CLOs that receive different ratings from two or more rating agencies, will be considered to have the higher credit rating. To the extent that the Fund invests in unrated CLO tranches, the Fund's ability to achieve its investment objective will be more dependent on Fund management's credit analysis than would be the case when the Fund invests in rated CLO tranches.

Further, interest on certain tranches of a CLO may be paid in kind or deferred and capitalized (paid in the form of obligations of the same type rather than cash), which involves continued exposure to default risk with respect to such payments. Fund management may not be able to accurately predict how specific CLOs or the portfolio of underlying loans or bonds for such CLOs will perform based on financial models or react to changes or stresses in the market, including changes in interest rates.

CLOs, and their underlying loan obligations, are typically not registered for sale to the public and therefore are subject to certain restrictions on transfer and sale, potentially making them less liquid than other types of securities. Some unrated CLO securities may not have an active trading market or may be difficult to value. Additionally, when the Fund purchases a newly issued CLO security in the primary market (rather than from the secondary market), there often may be a delayed settlement period. As a result, the proceeds from the sale of CLO securities may not be readily available to make additional investments or to meet the Fund's redemption obligations. During a delayed settlement period, the liquidity of the CLO may be further reduced. During periods of limited liquidity and higher price volatility, the Fund's ability to acquire or dispose of CLO securities at a price and time the Fund deems advantageous may be impaired. To the extent the extended settlement process gives rise to short-term liquidity needs, the Fund may hold additional cash, sell investments or temporarily borrow from banks and other lenders. CLO securities are generally considered to

be long-term investments and there is no guarantee that an active secondary market will exist or be maintained for any given CLO security.

CLO Manager Risk. The CLOs in which the Fund invests are managed by investment advisers independent of BFA. CLO managers are responsible for selecting, managing and replacing the underlying bank loans or bonds within a CLO. CLO managers may have limited operating histories and may be subject to conflicts of interests, including managing the assets of other clients or other investment vehicles, or receiving fees that incentivize maximizing the yield, and indirectly the risk, of a CLO. Adverse developments with respect to a CLO manager, such as personnel and resource constraints, regulatory issues or other developments that may impact the ability and/or performance of the CLO manager, may adversely impact the performance of the CLO securities in which the Fund invests.

Debt Securities Risk. Debt securities, such as bonds, involve risks, such as credit risk, interest rate risk, extension risk, and prepayment risk, each of which are described in further detail below:

Credit Risk. Credit risk refers to the possibility that the issuer of a debt security (i.e., the borrower) will not be able to make payments of interest and principal when due. Changes in an issuer's credit rating or the market's perception of an issuer's creditworthiness may also affect the value of the Fund's investment in that issuer. The degree of credit risk depends on both the financial condition of the issuer and the terms of the obligation. For CLOs, the primary source of credit risk is the ability of the

underlying portfolio of loans or bonds to generate sufficient cash flow to pay investors on a full and timely basis when principal and/or interest payments are due. Default in payment on the underlying loans or bonds will result in less cash flow from the underlying portfolio and, in turn, less funds available to pay investors in the CLO.

Interest Rate Risk. The market value of bonds and other fixed-income securities changes in response to interest rate changes and other factors. Interest rate risk is the risk that prices of bonds and other fixed-income securities will increase as interest rates fall and decrease as interest rates rise.

The Fund may be subject to a greater risk of rising interest rates during a period of historically low interest rates. For example, if interest rates increase by 1%, assuming a current portfolio duration of ten years, and all other factors being equal, the value of the Fund's investments would be expected to decrease by 10%. (Duration is a measure of the price sensitivity of a debt security or portfolio of debt securities to relative changes in interest rates.) The magnitude of these fluctuations in the market price of bonds and other fixed-income securities is generally greater for those securities with longer maturities. Fluctuations in the market price of the Fund's investments will not affect interest income derived from instruments already owned by the Fund, but will be reflected in the Fund's net asset value. The Fund may lose money if short-term or long-term interest rates rise sharply in a manner not anticipated by Fund management.

To the extent the Fund invests in debt securities that may be prepaid at the

option of the obligor (such as mortgage-backed securities), the sensitivity of such securities to changes in interest rates may increase (to the detriment of the Fund) when interest rates rise. Moreover, 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.

These basic principles of bond prices also apply to U.S. Government securities. A security backed by the "full faith and credit" of the U.S. Government is guaranteed only as to its stated interest rate and face value at maturity, not its current market price. Just like other fixed-income securities, government-guaranteed securities will fluctuate in value when interest rates change.

A general rise in interest rates has the potential to cause investors to move out of fixed-income securities on a large scale, which may increase redemptions from funds that hold large amounts of fixed-income securities. Heavy redemptions could cause the Fund to sell assets at inopportune times or at a loss or depressed value and could hurt the Fund's performance.

Extension Risk. When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these obligations to fall.

Prepayment Risk. When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Fund may

have to invest the proceeds in securities with lower yields. CLOs are typically structured such that, after a specified period of time, the majority investor in the equity tranche can call (i.e., redeem) the securities issued by the CLO in full. The Fund may not be able to accurately predict when or which of its CLO investments may be called, resulting in the Fund having to reinvest the proceeds in unfavorable circumstances or lower-yielding CLOs, which in turn could cause in a decline in the Fund's income.

Assets Under Management (AUM) Risk. From time to time, an Authorized Participant (as defined in the Creations and Redemptions section of the Fund's prospectus (the "Prospectus")), a third-party investor, the Fund's adviser, an affiliate of the Fund's adviser, or another fund may invest in the Fund and hold its investment for a specific period of time to allow 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.

Authorized Participant Concentration Risk. Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund. There are a limited number of institutions that may act as Authorized Participants for the Fund, including on an agency basis on behalf of other market participants. No Authorized Participant is obligated to engage in creation or redemption transactions. To the extent that Authorized Participants exit the business or do not place creation or redemption orders for the Fund and no other Authorized

Participant places orders, Fund shares are more likely to trade at a premium or discount to NAV and possibly face trading halts or delisting.

Cash Transactions Risk. The Fund may effect some or 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.

Covenant Lite Loans Risk. Certain of the underlying loans in which a CLO may invest may be issued or offered as "covenant lite" loans, which have few or no financial maintenance covenants that would require a borrower to maintain certain financial metrics. Because covenant lite loans contain few or no financial maintenance covenants, they may not include terms that permit the lender of the loan to monitor the borrower's financial performance and, if certain criteria are breached, declare a default, which would allow the lender to restructure the loan or take other action intended to help mitigate losses. As a result, a CLO could experience relatively greater difficulty or delays in enforcing its rights on its holdings of covenant lite loans than its holdings of loans or securities with financial maintenance covenants, which may result in losses, especially during a downturn in the credit cycle.

High Portfolio Turnover Risk. The Fund may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) 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. The sale of Fund portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies, such as index ETFs. These effects of higher than normal portfolio turnover may adversely affect Fund performance.

Illiquid Investments Risk. The Fund may not acquire any illiquid investment if, immediately after the acquisition, the Fund would have invested more than 15% of its net assets in illiquid investments. An illiquid investment is any investment that the Fund reasonably expects cannot be sold or disposed of in current market conditions in seven calendar days or less without the sale or disposition significantly changing the market value of the investment. Liquid investments may become illiquid after purchase by the Fund, particularly during periods of market turmoil. There can be no assurance that a security or instrument that is deemed to be liquid when purchased will continue to be liquid for as long as it is held by the Fund, and any security or instrument held by the Fund may be deemed an illiquid investment pursuant to the Fund's liquidity risk management program. The Fund's illiquid investments may reduce the returns of the Fund because it may be difficult to sell the illiquid investments at an advantageous time

or price. In addition, if the Fund is limited in its ability to dispose of illiquid investments during periods when shareholders are redeeming or selling their shares or the Fund's net assets otherwise shrink, the Fund will need to dispose of liquid securities to meet redemption requests and illiquid securities will become a larger portion of the Fund's holdings. An investment may be illiquid due to, among other things, the reduced number and capacity of traditional market participants to make a market in fixed-income securities or the lack of an active trading market. To the extent that the Fund's principal investment strategies involve derivatives or securities with substantial market and/or credit risk, the Fund will tend to have greater exposure to the risks associated with illiquid investments. 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. This may be magnified in a rising interest rate environment or other circumstances where investor redemptions or sales of Fund shares may be higher than normal. In addition, when there is illiquidity in the market for certain securities, the Fund, due to limitations on illiquid investments, may be subject to purchase and sale restrictions. During periods of market volatility, liquidity in the market for the Fund's shares may be impacted by the liquidity in the market for the underlying securities or instruments held by the Fund, which could lead to the Fund's shares trading at a premium or discount to the Fund's NAV.

Issuer Risk. Fund performance depends on the performance of individual securities to which the Fund has exposure. Changes in the financial condition or credit rating of an issuer of those securities may cause the value of the securities to decline.

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.

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 and Selection Risk. Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. The value of a security or other asset may decline due to changes in general market conditions, economic trends or events that are not specifically related to the issuer of the security or other asset, or factors that affect a particular issuer or issuers, exchange, country, group of countries, region, market, industry, group of industries, sector or asset class. Local, regional or global events such as war, acts of terrorism, the spread of infectious illness or other public health issues like pandemics or epidemics, recessions, or other events could have a significant impact on the Fund and its investments. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.

Recent policy initiatives undertaken by the U.S. government have the potential to impact international relations, trade agreements and the overall regulatory environment in ways that could create uncertainty and instability in domestic and global markets, and could adversely affect the investment performance of the Fund. In particular, actions taken by the U.S. government in respect of international trade relations could lead to trade wars, increased costs for imported goods, disruptions in supply chains, reduced foreign investment, and instability in regions where the Fund invests.

Market Trading Risk. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares (including through a trading halt), losses from trading in secondary markets, periods of high volatility, and disruptions in the process of creating and redeeming Fund shares. Any of these factors, among others, may lead to the Fund's shares trading in the secondary market at a premium or discount to NAV or to the intraday value of the Fund's portfolio holdings. If you buy Fund shares at a time when the market price is at a premium to NAV or sell Fund shares at a time when the market price is at a discount to NAV, you may pay significantly more or receive significantly less than the underlying value of the Fund shares.

Non-Diversification Risk. The Fund is a non-diversified fund. Because the Fund may invest in securities of a smaller number of issuers, it may be more exposed to the risks associated with and developments affecting an individual issuer than a fund that invests more widely.

Operational and Technology Risks. The Fund is directly and indirectly susceptible to operational and technology risks, including those related to human errors, processing errors, communication errors, systems failures, cybersecurity incidents, and the use of artificial intelligence and machine learning ("AI"), which may result in losses for the Fund and its shareholders or may impair the Fund's operations. While the Fund's service providers are required to have appropriate operational, information security and cybersecurity risk management policies and procedures, their methods of risk management may differ from those of the Fund. Operational and technology risks for the issuers in which the Fund invests could also result in material adverse consequences for such issuers and may cause the Fund's investments in such issuers to lose value.

Risk of Investing in the United States. 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.

Structured Securities Risk. Because structured securities of the type in which the Fund may invest typically involve no credit enhancement, their credit risk generally will be equivalent to that of the underlying instruments, index or reference obligation and will also be subject to counterparty risk. The Fund may have the right to receive payments only from the structured security, and generally does not have direct rights against the issuer or the entity that sold the assets to be securitized. In addition to the general risks associated with debt securities

discussed herein, structured securities carry additional risks, including, but not limited to: the possibility that distributions from collateral securities will not be adequate to make interest or other payments; the quality of the collateral may decline in value or default; and the possibility that the structured securities are subordinate to other classes. The Fund is permitted to invest in a class of structured securities that is either subordinated or unsubordinated to the right of payment of another class. Subordinated structured securities typically have higher yields and present greater risks than unsubordinated structured securities. Structured securities are typically sold in private placement transactions, and there currently is no active trading market for structured securities. Structured securities are based upon the movement of one or more factors, including currency exchange rates, interest rates, reference bonds and stock indices, and changes in interest rates and impact of these factors may cause significant price fluctuations. Additionally, changes in the reference instrument or security may cause the interest rate on the structured security to be reduced to zero. Certain issuers of such structured securities may be deemed to be "investment companies" as defined in the Investment Company Act. As a result, the Fund's investment in such securities may be limited by certain investment restrictions contained in the Investment Company Act.

Variable and Floating Rate Instrument Risk. Variable and floating rate securities provide for periodic adjustment in the interest rate paid on the securities. Securities with floating or variable interest rates can be less sensitive to

interest rate changes than securities with fixed interest rates, but may decline in value if their coupon rates do not reset as high, or as quickly, as comparable market interest rates, and generally carry lower yields than fixed securities of the same maturity. These securities will not generally increase in value if interest rates decline. A decline in interest rates may result in a reduction in income received from variable and floating rate securities held by the Fund and may adversely affect the value of the Fund's shares. These securities may be subject to greater illiquidity risk than other fixed income securities, meaning the absence of an active market for these securities could make it difficult for the Fund to dispose of them at any given time. Floating rate securities generally are subject to legal or contractual restrictions on resale, may trade infrequently, and their value may be impaired when the Fund needs to liquidate such loans. Benchmark interest rates may not accurately track market interest rates. Although floating rate securities are less sensitive to interest rate risk than fixed-rate securities, they are subject to credit risk and default risk, which could impair their value.

When-Issued and Delayed Delivery Securities and Forward Commitments Risk. When-issued and delayed delivery securities and forward commitments involve the risk that the security the Fund buys will lose value prior to its delivery. There also is the risk that the security will not be issued or that the other party to the transaction will not meet its obligation. If this occurs, the Fund may lose both the investment opportunity for the assets it set aside to pay for the security and any gain in the security's price.

Management

Investment Adviser. BlackRock Fund Advisors.

Portfolio Managers. Saffet Ozbalci, CFA, Peter Hirsh, Nidhi Patel and Tyler Debussey (the "Portfolio Managers") are jointly and primarily responsible for the day-to-day management of the Fund. Messrs. Ozbalci, Hirsh and Debussey and Ms. Patel have been Portfolio Managers of the Fund since 2023, 2022, 2024 and 2022, respectively.

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 you 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.