The fund will invest at least 80% of its assets in the component securities of the index, and it will invest at least 90% of its assets in fixed income securities of the types included in the underlying index that BFA believes will help the fund track the 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 index as well as in fixed income securities other than the types included in the index, but which BFA believes will help the fund track the index.