1、This is a set of reverse system parts for vehicles to ensure drivers' backup parking safety 2、Provide 4 ultrasonic sensors, which is of high sensibility, to ensure your traffic security and personal safety 3、Comes with buzzing alarm for safe warning 4、Self-inspection system, can automatically check abnormal condition itself, avoiding reversing collision 5、With a drill head, convenient to drill hole. Easy installation and operation Features: This is a set of reverse system parts for vehicles to ensure drivers' backup parking safety. Provide 4 ultrasonic sensors, which is of high sensibility, to ensure your traffic security and personal safety. Comes with buzzing alarm for safe warning. Self-inspection system, can automatically check abnormal condition itself, avoiding reversing collision. With a drill head, convenient to drill hole. Easy installation and operation. Specifications: Material: Plastic + pcb + electronic components Sensor Color: Silver, White, Black(optional) Rate voltage: DC 12V Ultrasonic frequency: 40KHz Detecting distance: 0.3-2.5m (0.98-8.2ft) Buzzer size: Approx. 44 * 17mm / 1.73'' * 0.67'' Main control box size: Approx. 90 * 60 * 23mm / 3.54'' * 2.36'' * 0.9'' Weight: Approx. 360g Package includes: 1 * Main Control Box 1 * Buzzing Alarm Device 4 * Sensors with Line 1 * Hole Saw 1 * Power Cable 2 * Double Side Stickers Note: It is easy to install, but professional installation is highly recommended.