The Ultrasonic Side Mirror Sensor safely guides your car into and out of the garage. Cordless and easy to install, it illuminates green to indicate it is clear to enter. A bright yellow light indicates when your side view mirror is getting close to the garage opening. A bright red light and siren indicate you are too far over and in danger of damaging your vehicle. Features adjustable settings (4” to 24” from wall) for a perfect park every time.