The T. Rowe Price QM U.S. Bond Index Fund I Class (TSBLX) is a mutual fund that focuses on investing in a diverse portfolio of high-quality, investment-grade bonds issued by U.S. companies. This fund is managed by T. Rowe Price, a reputable investment management firm, and aims to track the performance of a specific bond index. As an "I Class" fund, it is designed for institutional investors and has a lower expense ratio compared to other classes of the same fund. This mutual fund offers investors a low-cost and efficient way to gain exposure to the U.S. bond market.