This Top Dawg Audible Backup Sensor System includes 4 rear sensors that will alert the driver audibly if there is an object within 6 feet of vehicle when vehicle is in reverse. As driver moves closer to objects, the frequency of the audible alert increases, and when vehicle is within 1 foot of object, the beep is continuous. This system is designed for cars, SUVs and some trucks. Power is supplied by tapping into reverse back lights. This unit includes controller/computer unit, Speaker with mute switch and 16 ft. cable, four (4) rear sensors available in white, black or unpainted with 8 ft. cable, drill bit, eight (8) five (5) degree angled wedges and installation guide. Installation is required and can be done DIY in about 1 hour or you can pay a professional installer to install this unit.