The Fund seeks to track the investment results of the Bloomberg Barclays MSCI Global Green Bond Select (USD Hedged) Index (the “Underlying Index”), which measures the performance of global investment-grade (as determined by Bloomberg Index Services Limited, a subsidiary of Bloomberg Barclays Capital, Inc. (the “Index Provider” or “Bloomberg Barclays”)) green bonds issued to fund projects with direct environmental benefits. Green bonds are fixed income securities, the proceeds of which are exclusively and formally applied to projects or activities that promote climate or other environmental sustainability purposes. For inclusion in the Underlying Index, securities are independently evaluated by MSCI ESG Research LLC (“MSCI ESG Research”), pursuant to an agreement between MSCI ESG Research and Bloomberg Index Services Limited (or an affiliate), based on four criteria specified in the Green Bond Principles published by MSCI ESG Research (“Green Bond Principles”). The first criterion for bond eligibility in the Underlying Index is an evaluation of whether the use of proceeds falls within at least one of six eligible environmental categories defined by MSCI ESG Research (i.e., alternative energy, energy efficiency, pollution prevention and control, sustainable water, green building, and climate adaption). The remaining three criteria for evaluation and inclusion in the Underlying Index are the existence of processes for green project evaluation and selection, the existence of processes for management of proceeds, and the existence of a commitment to ongoing reporting of the environmental impact. Both self-labeled green bonds and unlabeled bonds are evaluated using these criteria for potential inclusion in the Underlying Index. So long as projects fall within an eligible MSCI ESG Research green bond category and there is sufficient transparency on the use of proceeds, a bond is considered for the Underlying Index even if it is not explicitly marketed as a green bond. Meeting all four criteria is required for bonds issued after the publication of the Green Bond Principles in January 2014. Green bonds issued prior to 2014 that are widely accepted by investors as green bonds may still qualify for the Underlying Index, even if not all four principles are satisfied, since no formal guidelines were available to issuers at the time of issuance. The Underlying Index includes sovereign and government-related debt, corporate bonds and securitized bonds denominated in currencies determined by the Index Provider from both developed and emerging market issuers. As of October 31, 2020, the Underlying Index was comprised of securities issued by entities in the following 38 countries as well as securities issued or guaranteed by supranational entities: Australia, Austria, Belgium, Brazil, Canada, Chile, China, Czech Republic, Denmark, Finland, France, Germany, Hong Kong, Hungary, India, Indonesia, Ireland, Italy, Japan, Lithuania, Luxembourg, Mexico, the Netherlands, Norway, the Philippines, Poland, Portugal, Romania, Russia, Saudi Arabia, Singapore, South Korea, Spain, Sweden, Switzerland, the United Arab Emirates, the U.K. and the U.S. As of October 31, 2020, a significant portion of the Underlying Index is represented by financials, sovereign and quasi-sovereign debt obligations and non-U.S. agency debt securities. The components of the Underlying Index are likely to change over time. The Underlying Index includes fixed-rate coupon bonds and bonds that convert from fixed to floating rate, including fixed-to-float perpetuals. Fixed-to-floating rate bonds are eligible during their fixed-rate term only. Certain types of securities, such as bonds with equity type features (e.g., warrants, convertibles, and preferreds), inflation-linked bonds, floating-rate issues, fixed-rate perpetuals, tax-exempt municipal securities, private placements (other than those offered pursuant to Rule 144A or Regulation S promulgated under the Securities Act of 1933, as amended (the “1933 Act”)) and retail bonds, are excluded from the Underlying Index. The Underlying Index will hold bonds until final maturity. As of October 31, 2020, the weighted average duration of the securities in the Underlying Index was 8.21 years and the weighted average maturity of the securities in the Underlying Index was 9.20 years. The securities in the Underlying Index are updated on the last business day of each month (the rebalancing date), and the currency risk of the securities in the Underlying Index is hedged to the U.S. dollar on a monthly basis. 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 or other instruments comprising 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 and other components of the Underlying Index. The Fund generally will invest at least 90% of its assets in the component securities and other instruments 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 and other instruments 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. Components of the Underlying Index include fixed-income securities and foreign currency forward contracts (both deliverable and non-deliverable) designed to hedge non-U.S. currency fluctuations against the U.S. dollar. The notional exposure to foreign currency forward contracts (both deliverable and non-deliverable) generally will be a short position that hedges the currency risk of the fixed-income portfolio. The Fund seeks to track the investment results of the Underlying Index before fees and expenses of the Fund. The Underlying Index sells forward the total value of the underlying non-U.S. dollar currencies at a one-month forward rate to hedge against fluctuations in the relative value of the non-U.S. dollar component currencies in relation to the U.S. dollar. The hedge is reset on a monthly basis. The Underlying Index is designed to have higher returns than an equivalent unhedged investment when the non-U.S. dollar component currencies are weakening relative to the U.S. dollar and appreciation in some of the non-U.S. dollar component currencies does not exceed the aggregate depreciation of the others. Conversely, the Underlying Index is designed to have lower returns than an equivalent unhedged investment when the non-U.S. dollar component currencies, on a net basis, are rising relative to the U.S. dollar. In order to track the “hedging” component of the Underlying Index, the Fund enters into foreign currency forward contracts designed to offset the Fund’s exposure to the non-U.S. dollar component currencies. A currency forward contract is a contract between two parties to buy or sell a specified amount of a specific currency in the future at an agreed-upon exchange rate. The Fund’s exposure to foreign currency forward contracts is based on the aggregate exposure of the Fund to the non-U.S. dollar component currencies. While this approach is designed to minimize the impact of currency fluctuations on Fund returns, it does not necessarily eliminate the Fund’s exposure to the non-U.S. dollar component currencies. The return of the currency forward contracts may not perfectly offset the actual fluctuations in value between the non-U.S. dollar component currencies and the U.S. dollar. The Fund may also use non-deliverable forward (“NDF”) contracts to execute its hedging transactions. An NDF is a contract where there is no physical settlement of two currencies at maturity. Rather, based on the movement of the currencies and the contractually agreed-upon exchange rate, a net cash settlement will be made by one party to the other in U.S. dollars. 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 Barclays, MSCI ESG Research, or their affiliates, which are 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 isconcentrated. 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.