The underlying index consists of publicly-issued U.S. Treasury securities that have a remaining maturity of greater than or equal to one year and less than three years and have $300 million or more of outstanding face value, excluding amounts held by the Federal Reserve System. 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.