Fidelity Flex U.S. Bond Index Fund (FIBUX) is a mutual fund that seeks to track the performance of the U.S. bond market. It invests in a diverse portfolio of high-quality bonds, providing investors with a low-cost and efficient way to gain exposure to the U.S. fixed income market. This fund is managed by Fidelity Investments, a reputable and experienced investment management company. FIBUX is a suitable option for investors looking for a passive approach to bond investing with the potential for steady income and capital preservation.