20 The rear radar receiver is mounted to the bottom inside of the bumper. We used a urethane window sealer as an adhesive to stick the receiver to the bumper. Remember, it can be mounted behind fiberglass or plastic, but not metal. The rear receiver wires differently because it has no Laser Defuser, which is optional. On this system, we do not have the rear radar defusing option, but you can add it to any system.