"RD2 KIT IS USED WITH THE 400MHZ RF/GPS COMMUNICATION CHANNELS. IT IS COMPATIBLE WITH THE DF12 CONTROLLER, DF5 CONTROLLER AND THE HHDR. IT CONTAINS THE NAVIGATIONAL DEVICE (RD2) ALONG WITH SUPPORTING CABLES, RF ANTENNA, BATTERY PACK AND ASSOCIATED SOFTWARE FOR RD2; LENGTH: 5.00 INCHES; WIDTH: 5.00 INCHES; HEIGHT: 3.00 INCHES; WEIGHT: 3.00 POUNDS."