The investment seeks daily investment results, before fees and expenses, that correspond to the inverse (-1x) of the daily performance of the Barclays U.S. 20+ Year Treasury Bond Index. The fund invests in derivatives that ProShare Advisors believes, in combination, should have similar daily return characteristics as the inverse (-1x) of the daily return of the index. The index includes all publicly issued, U.S. Treasury securities that have a remaining maturity greater than 20 years, are non-convertible, are denominated in U.S. dollars, are rated investment grade, are fixed rate, and have more than $250 million par outstanding. The fund is non-diversified