iShares Prime Money Market ETF (PMMF) is an exchange-traded fund in the Prime Money Market category. It has $748.83M in assets, an expense ratio of 0.20% and a 3.98% dividend yield. The fund seeks to achieve its investment objective by investing, under normal circumstances, in a broad range of U.S. dollar-denominated money market instruments, including government, U.S. and foreign bank, and commercial obligations and repurchase agreements.