The investment seeks to track the investment results of the S&P AMT-Free Municipal Series Dec 2025 IndexTM composed of investment-grade U.S. municipal bonds maturing after December 31, 2024 and before December 2, 2025. The index includes municipal bonds primarily from issuers that are state or local governments or agencies such that the interest on the bonds is exempt from U.S. federal income taxes and the federal AMT. The fund generally will invest at least 90% of its assets in the component securities of the index, except during the last months of the fund's operations.