Universal design: suitable for any car, SUV, truck. Wireless design, no damage to the original car wiring, just stick it on the car door. Warning how it works. When the door is open, blue light flashes to warn the rear pedestrians or vehicles to avoid accident or collision. 3 flashing modes ----- 0-7 sec. All LEDs flash rapidly. 7-60 sec. 7-60 sec: Each LED flashes sequentially. 60-110 sec. Each Led flashes slowly rotating. 110 sec. automatic power off. Waterproof design: submerged in water for 30 minutes and still works. High-tech components sensing: controlled by infrared chip program to improve the sensitivity and keep the stability of the product. Long battery life: This product uses CR2032 button battery (battery is included), through testing, in normal working condition, can be used for 1-1.5 years, screw cap design, you can easily replace the battery.