Allows easy access to factory radios with built-in rear speaker outputs. Plugs directly into an empty 35-pin socket on back of radio. 4-pin plug also plugs into rear input on NCA 450-AA amplifier. Wires are clearly labelled for easy installation. NOTE: This plug accesses the speaker leads of the radio but does not activate your radio's built-in fader control. To have your fader enables, you must go to a H-D dealer and have your radio "re-flashed.".