Strategy. The Fund seeks to track the investment results of the BlackRock Interest Rate Hedged U.S. Aggregate Bond Index (the Underlying Index ), which is designed to minimize the interest rate risk exposure of a portfolio composed of U.S. dollar-denominated, investment-grade bonds, represented in the Underlying Index by the Underlying Fund, by including a series of up to 10 interest rate swap contracts with different maturities (as determined by BlackRock Index Services, LLC (the Index Provider )). As of October 31, 2025, the Underlying Index includes approximately 12 components, as well as a cash position that is intended to reflect the collateral that must be held to manage the swaps positions. The Fund invests in U.S. dollar-denominated, investment-grade bonds primarily through … Show more… The Fund seeks to track the investment results of the BlackRock Interest Rate Hedged U.S. Aggregate Bond Index (the Underlying Index ), which is designed to minimize the interest rate risk exposure of a portfolio composed of U.S. dollar-denominated, investment-grade bonds, represented in the Underlying Index by the Underlying Fund, by including a series of up to 10 interest rate swap contracts with different maturities (as determined by BlackRock Index Services, LLC (the Index Provider )). As of October 31, 2025, the Underlying Index includes approximately 12 components, as well as a cash position that is intended to reflect the collateral that must be held to manage the swaps positions. The Fund invests in U.S. dollar-denominated, investment-grade bonds primarily through its investment in the Underlying Fund. To be included in the Underlying Fund, securities must have $300 million or more of outstanding face value and must have at least one year remaining to maturity, with the exception of amortizing securities such as mortgage-backed securities ( MBS ) and asset-backed securities ( ABS ), which have lower thresholds as defined by the Underlying Fund's index provider. The Fund seeks to track the interest rate hedging component of the Underlying Index primarily through the use of positions in interest rate swaps ( i.e ., contracts in which the Fund makes fixed-rate payments while receiving floating-rate payments based on a reference rate). The different maturities and weights of the swap contracts included in the Underlying Index are intended to hedge the portfolios duration exposure ( i.e ., sensitivity to changes in interest rates) at key points on the yield curve, as determined by the Index Provider. The Underlying Index includes a fixed number of shares (to be adjusted in the event of any stock splits) of the Underlying Fund, and the Index Provider rebalances the weights of the swap contracts included in the Underlying Index daily. On a monthly basis, the Index Provider will add new swap contracts to the Underlying Index and remove the previous months swap contracts. The Fund seeks to achieve its investment objective by investing, under normal circumstances, at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in component securities and instruments in the Funds Underlying Index. Cash and cash equivalent investments associated with a derivative position will be treated as part of that position for the purposes of calculating the percentage of investments included in the Underlying Index. The Fund seeks to track the investment results of the Underlying Index before fees and expenses of the Fund. The Fund may also invest in other interest rate futures contracts, including but not limited to, U.S. Treasuries, Eurodollar and Federal Funds futures. The Funds interest rate swap and futures positions are not intended to mitigate credit risk or other factors influencing the price of U.S. dollar-denominated, investment-grade bonds, which may have a greater impact than interest rates. The CFTC has adopted certain requirements that subject registered investment companies and their advisers to regulation by the CFTC if a registered investment company invests more than a prescribed level of its net asset value in CFTC-regulated futures, options and swaps, or if a registered investment company markets itself as providing investment exposure to such instruments. Due to the Funds use or potential use of such instruments above the prescribed levels, it is considered a commodity pool under the Commodity Exchange Act ( CEA ). BFA is considered a commodity pool operator ( CPO ) with respect to the Fund and is subject to regulation by the CFTC and the National Futures Association ( NFA ). BFA uses an indexing approach to try to achieve the Funds investment objective. The Fund does not try to beat the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. Indexing may eliminate the chance that the Fund will substantially outperform the Underlying Index but also may reduce some of the risks of active management, such as poor security selection. Indexing seeks to achieve lower costs and better after-tax performance by aiming to keep portfolio turnover low in comparison to actively managed investment companies. BFA uses a representative sampling indexing strategy to manage the Fund and the Underlying Fund. Representative sampling is an indexing strategy that involves investing in a representative sample of securities or other instruments that collectively has an investment profile similar to that of an applicable underlying index. The instruments selected are expected to have, in the aggregate, investment characteristics (based on factors such as market value and industry weightings), fundamental characteristics (such as return variability, duration ( i.e. , an instrument's price sensitivity to a change in interest rates), maturity or credit ratings and yield) and liquidity measures similar to those of an applicable underlying index. The Fund or the Underlying Fund may or may not hold all of the components of the applicable Underlying Index. 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). The Underlying Index is sponsored by the Index Provider, ? an affiliated person of the Fund and of BFA, the Funds investment adviser. The Index Provider determines the composition and relative weightings of the components of the Underlying Index and publishes information regarding the market value of the Underlying Index. 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) and repurchase agreements collateralized by U.S. government securities are not considered to be issued by members of any industry. Show less