The investment seeks to track the investment results of the ICE BofA BB US High Yield Constrained Index composed of BB, or equivalently rated, fixed rate U.S. dollar-denominated bonds issued by U.S. and non-U.S. corporations. 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 (BlackRock Cash Funds), as well as in securities not included in the index, but which BFA believes will help it track the index.