Size:6.60in. x 6.60in. x 3.90in. The Crimestopper PARK-EMCU rear parking assist system for vehicles with plastic bumpers offers an audible chime as you approach an object. The system comes with 4 paintable ultrasonic sensors that are IP68 waterproof. They alert when you are pulling in or backing up. The system progressively increases the audible alert as the vehicle comes closer to the object.