Specific adapter to replace an original Mercedes Audio 20 car radio with a Mercedes-Benz Comand 2.5 HDD navigation system High-quality plug & play wiring Easy installation Scope of delivery: Adapter Note: A GPS antenna is also required - item no. 33821 Depending on the vehicle you will also need this - item no. 37014 The 4 pin connector goes to the rear view mirror microphone.