The Fund seeks to track the investment results of the Bloomberg Barclays US Floating Rate Note < 5 Years Index (the “Underlying Index”), which measures the performance of U.S. dollar-denominated, investment-grade (as determined by Bloomberg Index Services Limited (the “Index Provider” or “Bloomberg”)) floating rate notes. Securities in the Underlying Index have a remaining maturity of greater than or equal to one month and less than five years, and have $300 million or more of outstanding face value. As of October 31, 2020, a significant portion of the Underlying Index is represented by securities of companies in the financials industry or sector and corporate bonds and government related securities. As of October 31, 2020, the Underlying Index was comprised of securities of companies in the following countries or regions: Australia, Canada, China, Denmark, Finland, France, Germany, Hong Kong, Italy, Japan, the Netherlands, New Zealand, Norway, Singapore, South Korea, Spain, Sweden, Switzerland, the United Kingdom (the “U.K.”) and the U.S. The components of the Underlying Index are likely to change over time. The Underlying Index consists of debt instruments that pay a variable coupon rate, a majority of which are based on the 3-month London Interbank Offer Rate (“LIBOR”), with a fixed spread. The Underlying Index is market capitalization-weighted and the securities in the Underlying Index are updated on the last calendar day of each month. The Underlying Index may include U.S. registered, dollar-denominated bonds of non-U.S. corporations, governments and supranational entities. BFA 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. 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. “Representative sampling” is an indexing strategy that involves investing in a representative sample of securities that collectively has an investment profile similar to that of an applicable underlying index. The securities 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, maturity, credit ratings and yield) and liquidity measures similar to those of an applicable underlying index. The Fund may or may not hold all of the securities in the Underlying Index. The Fund generally will invest at least 90% of its assets in the component securities of the Underlying Index and may invest up to 10% of its assets in certain futures, options and swap contracts, cash and cash equivalents, including shares of money market funds advised by BFA or its affiliates (“BlackRock Cash Funds”), as well as in securities not included in the Underlying Index, but which BFA believes will help the Fund track the Underlying Index. From time to time when conditions warrant, however, the Fund may invest at least 80% of its assets in the component securities of the Underlying Index and may invest up to 20% of its assets in certain futures, options and swap contracts, cash and cash equivalents, including shares of BlackRock Cash Funds, as well as in securities not included in the Underlying Index, but which BFA believes will help the Fund track 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 lend securities representing up to one-third of the value of the Fund's total assets (including the value of any collateral received). The Underlying Index is sponsored by Bloomberg, which is independent of the Fund and BFA. 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. 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), repurchase agreements collateralized by U.S. government securities, and securities of state or municipal governments and their political subdivisions are not considered to be issued by members of any industry.