... 4. Designed for cars, suvs, 4x4s, vans, pickups, trucks, RVs, Trailers, and Buses. 5. Sensor Detection Range: ... when backing up 7. Each sensor with wedge-shaped plastic spacer for adjusting to non-vertical bumper surface ... 8. Perfect for backing up, street parking, parallel parking, ... 8 ohm, 0.5W Package contents: 4 x Ultrasonic Sensor 1 x Control Box/Unit 1 x Buzzer Warning ...