The Fund generally will invest at least 80 percent of its total assets in securities that comprise the Underlying Index. Strictly in accordance with its guidelines and mandated procedures, Invesco Indexing LLC (the Index Provider) compiles and maintains the Underlying Index. The Underlying Index seeks to measure the performance of a portfolio of U.S. dollar-denominated investment-grade municipal bonds with maturities or, in some cases, effective maturities, in the year 2028 (collectively, 2028 Bonds). Certain bonds in which the Fund may invest may contain embedded issuer call options. An embedded issuer call option means that the bonds issuer has the right to redeem a bond prior to its designated maturity date. Accordingly, the effective maturity date of a bond reflects an assessment of when that bond is likely to be called by the issuer, or in the alternate, the bonds stated maturity date (if it is not called by the issuer).