Strategy. The Fund seeks to track the investment results of the Russell Midcap Index (the Underlying Index), which measures the performance of the mid-capitalization sector of the U.S. equity market. The Underlying Index is a float-adjusted, capitalization-weighted index of equity securities issued by approximately 800 of the smallest issuers in the Russell 1000 Index. The Underlying Index includes equity securities issued by issuers with a median market cap of $11.91 billion as of October 31, 2025. Components primarily include industrials, consumer discretionary and financial companies, and may change over time. BlackRock 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 … Show more… The Fund seeks to track the investment results of the Russell Midcap Index (the Underlying Index), which measures the performance of the mid-capitalization sector of the U.S. equity market. The Underlying Index is a float-adjusted, capitalization-weighted index of equity securities issued by approximately 800 of the smallest issuers in the Russell 1000 Index. The Underlying Index includes equity securities issued by issuers with a median market cap of $11.91 billion as of October 31, 2025. Components primarily include industrials, consumer discretionary and financial companies, and may change over time. BlackRock 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 the Underlying Index. The securities selected are expected to have, in the aggregate, investment characteristics (based on factors such as market capitalization and industry weightings), fundamental characteristics (such as return variability and yield) and liquidity measures similar to those of the Underlying Index. The Fund may or may not hold all of the securities in the Underlying Index. The Fund generally invests at least 90% of its assets, plus the amount of any borrowing for investment purposes, in securities of the Underlying Index. Show less