The investment seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Barclays U.S. 20+ Year Treasury Bond Index (the "underlying index"). The fund generally invests at least 90% of its assets in the bonds of the underlying index and at least 95% of its assets in U.S. government bonds. The underlying index measures the performance of public obligations of the U.S. Treasury that have a remaining maturity of 20 or more years.