iShares Barclays MBS Bond Fund (the Fund), formerly iShares Lehman MBS Bond Fund, seeks investment results that correspond generally to the price and yield performance of the investment-grade agency mortgage-backed securities sector of the United States as defined by the Barclays Capital U.S. MBS Index (the Index). The Index measures the performance of investment-grade, fixed-rate, mortgage-backed, pass-through securities issued by the Government National Mortgage Association (GNMA), Federal National Mortgage Association (FNMA) and Federal Home Loan Mortgage Corporation (FHLMC). The Index includes securities issued by GNMA, FHLMC and FNMA that have 30, 20 and 15-year and balloon maturities that have a remaining maturity of at least one year, are investment grade and have more than $250 million or more of outstanding face value. The Index is a market capitalization-weighted index. The Fund’s investment advisor is BlackRock Fund Advisors.