The investment seeks daily investment results, before fees and expenses, that correspond to the inverse (-1x) of the daily performance of the ICE U.S. Treasury 20+ Year Bond Index. The fund invests in financial instruments that ProShare Advisors believes, in combination, should produce daily returns consistent with the fund's investment objective. The index includes publicly- issued U.S. Treasury securities that have a remaining maturity greater than or equal to twenty years and have $300 million or more of outstanding face value, excluding amounts held by the Federal Reserve. The fund is non-diversified.