The index is comprised of certain U.S. Treasury notes and bonds that are included in the Bloomberg US Treasury Index, along with principal only U.S. Treasury STRIPS. Under normal circumstances, the fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in a portfolio of U.S. Treasury securities that collectively have an average duration of approximately 20 years, either directly or indirectly (e.g., through derivatives). It is non-diversified.