The investment seeks to track the investment results (before fees and expenses) of the Invesco BulletShares® Municipal Bond 2021 Index. The fund generally will invest at least 80% of its total assets in securities that comprise the index. The index is designed to measure the performance of a portfolio of U.S. dollar-denominated investment-grade municipal bonds with maturities in the year 2021 or, in some cases, effective maturities in the year 2021. It is non-diversified.