Vanguard Extended Duration Treasury ETF (the Fund) is an exchange-traded share class of Vanguard Extended Duration Treasury Index Fund. The Fund employs a passive management or indexing investment approach designed to track the performance of the Lehman Brothers Treasury STRIPS 20–30 Year Equal Par Bond Index (the Index). The Index measures the investment return of Treasury STRIPS, coupon and principal, with maturities ranging from 20 to 30 years. A Treasury STRIP represents a single coupon payment, or a single principal payment, from a United States Treasury security that has been stripped into separately tradable components. The Fund will invest at least 80% of its assets in the United States Treasury securities held in its target Index. The Fund may invest in derivatives. The Vanguard Group, Inc., through its Fixed Income Group, serves as the investment advisor of the Fund.