The RiverNorth Managed Duration Municipal Income Fund Inc (ticker: RMM) is a mutual fund that focuses on investing in municipal bonds with varying durations. This fund is managed by RiverNorth Capital Management, LLC and aims to provide investors with a steady stream of tax-free income from the interest earned on these bonds. The fund's duration management strategy allows for potential capital appreciation while also mitigating interest rate risk. RMM is a suitable option for investors seeking tax-exempt income and a diversified portfolio of municipal bonds.