Strategy. The Fund seeks to track the investment results of the ICE U.S. Treasury Core Bond Index (the Underlying Index ), which measures the performance of public obligations of the U.S. Treasury. As of October 31, 2025, there were 294 issues in the Underlying Index. The Underlying Index consists of U.S. dollar-denominated sovereign debt publicly issued by the U.S. Treasury in its domestic market. Qualifying securities must have, as of the rebalancing date, a remaining term to final maturity of greater than one year. Index constituents also must have a fixed coupon schedule and an adjusted amount outstanding of at least $300 million, excluding amounts held by the Federal Reserve System Open Market Account ( SOMA ). Excluded from the Underlying … Show more… The Fund seeks to track the investment results of the ICE U.S. Treasury Core Bond Index (the Underlying Index ), which measures the performance of public obligations of the U.S. Treasury. As of October 31, 2025, there were 294 issues in the Underlying Index. The Underlying Index consists of U.S. dollar-denominated sovereign debt publicly issued by the U.S. Treasury in its domestic market. Qualifying securities must have, as of the rebalancing date, a remaining term to final maturity of greater than one year. Index constituents also must have a fixed coupon schedule and an adjusted amount outstanding of at least $300 million, excluding amounts held by the Federal Reserve System Open Market Account ( SOMA ). Excluded from the Underlying Index are inflation-linked securities, Treasury bills, agency debt issued with or without a government guarantee, original issue zero coupon securities and issues that have been stripped from coupon-paying bonds. However, the amounts outstanding of qualifying securities are not reduced by any individual components of such securities ( i.e. , coupon or principal) that have been stripped after inclusion in the Underlying Index. Securities issued or marketed primarily to retail investors do not qualify for inclusion in the Underlying Index. Index constituents are market value-weighted based on amounts outstanding reduced by amounts held by the Federal Reserve SOMA. Accrued interest is calculated assuming next-day settlement. Cash flows from bond payments and redemptions that are received during the month are retained in the Underlying Index until the end of the month and then are removed as part of the rebalancing. Cash does not earn any reinvestment income while it is held in the Underlying Index. The Underlying Index is rebalanced on the last calendar day of the month, based on information available up to and including the third business day before the last business day of the month. New issues must be auctioned on or before the calendar month end rebalancing date in order to qualify for the coming month. 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. 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 may or may not hold all of the components of the Underlying Index. The Fund will invest at least 80% of its assets in the component securities of the Underlying Index, and the Fund will invest at least 90% of its assets in U.S. Treasury securities that BFA believes will help the Fund track the Underlying Index. The Fund will invest no more than 10% of its assets in futures, options and swaps contracts that 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 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 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 owned, maintained and administered by ICE Data Indices, LLC (the Index Provider or IDI ), which is ? independent of the Fund and BFA. 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. Show less