The RM-300 is a hardware package required for the proper mounting of a single R300 RX receiver into a standard 19" audio rack (audio rack screws not included). Long bracket contains 2 removable plastic plugs (removal required when using SFMC-300 coax cable kit). The RM-300 can be oriented to either the left or right side of the R300 RX receiver. Tools needed (not supplied): T15 Torx driver.