Strategy. Principal Investment Strategies The Fund seeks to track the investment returns of its benchmark index, the Bloomberg U.S. Long Treasury Bond Index * . Under normal circumstances, the Fund invests at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in securities that are held in its benchmark index and at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in U.S. Treasury securities, which are backed by the full faith and credit of the U.S. Government. The Funds subadviser, T. Rowe Price Associates, Inc. (T. Rowe Price), invests the remainder of the Funds assets in other securities backed by the full faith and credit of the U.S. … Show more… Principal Investment Strategies The Fund seeks to track the investment returns of its benchmark index, the Bloomberg U.S. Long Treasury Bond Index * . Under normal circumstances, the Fund invests at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in securities that are held in its benchmark index and at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in U.S. Treasury securities, which are backed by the full faith and credit of the U.S. Government. The Funds subadviser, T. Rowe Price Associates, Inc. (T. Rowe Price), invests the remainder of the Funds assets in other securities backed by the full faith and credit of the U.S. Government and in shares of a T. Rowe Price internal money fund or short-term bond fund that invests exclusively in securities backed by the full faith and credit of the U.S. Government. Securities backed by the full faith and credit of the U.S. Government include, without limitation, securities issued by Government ? * Bloomberg and Bloomberg U.S. Long Treasury Bond Index are service marks of Bloomberg Finance L.P. and its affiliates, including Bloomberg Index Services Limited (BISL), the administrator of the index (collectively, Bloomberg) and have been licensed for use for certain purposes by MassMutual. Bloomberg is not affiliated with MassMutual, and Bloomberg does not approve, endorse, review, or recommend the Fund. Bloomberg does not guarantee the timeliness, accuracy, or completeness of any data or information relating to the Fund. ? National Mortgage Association and other government agencies and certain corporate debt securities guaranteed by U.S. Government agencies. The dollar-weighted average maturity of the Funds portfolio will normally exceed 10 years, and it will vary consistent with the dollar-weighted average maturity of the benchmark index. The Bloomberg U.S. Long Treasury Bond Index is an index consisting of U.S. dollar-denominated, fixed rate nominal debt issued by the U.S. Treasury with maturities of 10 years or more. The Fund does not attempt to fully replicate the index by holding each of the bonds represented in the index. Instead, the Fund seeks to track the returns of the index and more efficiently replicate the key risk factors of the index (such as maturity, duration, and credit quality) by attempting to capitalize on market inefficiencies through structural portfolio positioning and via small tactical bets on inflation, duration, and yield curve positioning. U.S. Treasury securities in which the Fund may invest include Treasury bills, notes, and bonds (which includes Treasury STRIPS), as well as Treasury inflation protected securities. The Fund buys and sells U.S. Treasury futures, which are futures contracts on U.S. Treasury bonds or notes, and options on such instruments, to gain efficient exposure to U.S. Treasury security prices, help realign the portfolio with the benchmark index, adjust its sensitivity to interest rate changes, and/or manage cash flows into and out of the Fund. Interest rate futures are also used to manage the Funds exposure to interest rate changes or to adjust portfolio duration. Use of derivatives by the Fund may create investment leverage. The Fund may purchase and sell securities on a when-issued, delayed delivery, to-be-announced, or forward commitment basis. The Fund may sell securities to better align its portfolio with the characteristics of the Bloomberg U.S. Long Treasury Bond Index and will generally seek to sell securities that have been removed from the index within a reasonable timeframe taking into consideration market conditions. The Fund expects that it will engage in active and frequent trading and so will typically have a relatively high portfolio turnover rate. Show less