The investment seeks to track the investment results of the Bloomberg Barclays U.S. Universal 5-10 Year Index. The fund generally will invest at least 90% of its assets in the component securities of the underlying index and may invest up to 10% 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. The index measures the performance of U.S. dollar-denominated taxable bonds that are rated either investment-grade or high yield with remaining effective maturities between five and ten years.