The Fund seeks to track the investment results of the Russell US Small Cap Factors Blend Style Index (the “Underlying Index”), which is an objective, rules-based equity index provided by FTSE Russell (the “Index Provider” or “Russell”). The Underlying Index is designed to select equity securities from the Russell 2000® Index (the “Parent Index”), with exposure to five equity style factors (momentum, quality, value, size and low volatility) while maintaining a level of risk similar to that of the Parent Index. The Parent Index, which measures the performance of the small-capitalization segment of the U.S. equity market, is a float-adjusted capitalization-weighted index consisting of approximately 2000 of the smallest issuers in the Russell 3000 Index. Russell, in selecting equity securities from the Parent Index, assigns a weighted composite score for a security using a proprietary model based on five commonly-used equity style factors (momentum, quality, value, size and low volatility). The value score is calculated from the following value factor metrics: 12-month trailing book-to-price, dividend yield, earnings yield and cash flow yield (i.e., cash flow divided by the full market capitalization). The momentum score is calculated from three momentum factor metrics: price momentum, earnings momentum and earnings announcement drift (i.e., the difference between a stock's performance on and immediately following an earnings announcement date). The quality score is calculated from four quality factor metrics: gross profitability, dilution, accruals and changes in net operating assets. The low volatility score is calculated based on a 12-month trailing realized volatility, and the size score seeks to measure the market capitalization of a company as compared to other companies of the Parent Index. The Underlying Index excludes constituents in the Parent Index that rank in the least liquid 20%, as determined by the Index Provider (i.e., approximately 400 constituents). As of March 31, 2021, a significant portion of the Underlying Index is represented by securities of companies in the consumer discretionary, financials and healthcare industries or sectors. The components of the Underlying Index are likely to change over time. The Underlying Index is reviewed monthly using an optimization process designed to maximize, in aggregate, the Underlying Index's exposure to the weighted combination of the five target investment style factors while maintaining total risk similar to that of the Parent Index. 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 capitalization and industry weightings), fundamental characteristics (such as return variability 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 80% of its assets in the component securities of its Underlying Index and in investments that have economic characteristics that are substantially identical to the component securities of its Underlying Index (i.e., depositary receipts representing 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 money market funds advised by BFA or its affiliates, as well as in securities not included in the Underlying Index, but which BFA believes will help the Fund track the 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 investments not 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 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 Russell, which is part of the London Stock Exchange Group and 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) and repurchase agreements collateralized by U.S. government securities are not considered to be issued by members of any industry.