The Invesco VRDO Tax-Free ETF (Fund) is based on the ICE US Municipal AMT-Free VRDO Constrained Index (Index). The Fund generally will invest at least 80% of its total assets in U.S. dollar tax-exempt variable rate demand obligations (VRDOs). The Index tracks the performance of U.S. dollar tax-exempt VRDOs that are publicly issued by U.S. states and territories, and their political subdivisions, and that have interest rates that reset daily, weekly or monthly. The Fund does not purchase all of the securities in the Index; instead, the Fund utilizes a 'sampling' methodology to seek to achieve its investment objective. The Fund and the Index are rebalanced on the last calendar day of the month.