iShares Core 1-5 Year USD Bond ETF seeks to track the investment results of the Bloomberg U.S. Universal 1-5 Year Index, which measures the performance of U.S. dollar-denominated taxable bonds that are rated either investment-grade or high yield with remaining effective maturities between one and five years. The fund will invest at least 80% of its assets in the component securities of the index and TBA transactions that have economic characteristics that are substantially identical to the economic characteristics of 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 index.