This is an HPI Reverse Module for the HPI Savage X, XL, 21, 25, and Savage SS trucks.  This allows the Savage to operate in two or three speeds of reverse when using a 3-channel radio system and a servo for shifting.  This works with the 3-speed transmission.  Included is the pre-assembled reverse module, all hardware (linkages, screw, collars, etc) for hook up, and detailed step by step instructions.