iShares 20+ Year Treasury Bond ETF (the Fund) is an exchange-traded fund. The Fund seeks to track the investment results of an index composed of United States Treasury bonds with remaining maturities greater than 20 years. The Fund seeks to track the investment results of the Barclays U.S. 20+ Year Treasury Bond Index (the Underlying Index), which measures the performance of public obligations of the United States Treasury that have a remaining maturity of 20 or more years. The Underlying Index includes all publicly-issued the United States Treasury securities that have a remaining maturity of greater than or equal to 20 years. BlackRock Fund Advisors serves as investment adviser of the Fund.