UNIVERSAL DESIGN: Fit for any cars, SUV, truck. Wireless design, do not destroy the original car lines, only need to stick them at the door. HOW THE WARNING WORK: When the door opened, the blue light flashing, warning the rear pedestrian or vehicle, to avoid accident or collision. 3 MODES FLASHING----- 0-7 Seconds: All Led Rapid Flashing. 7-60 Seconds: Each Led Sequential Flashing. 60-110 seconds: Each Led Slow Swirl Flashing. Automatic power off after 110 second. WATERPROOF DESIGN: Soaked in water for 30 minutes, still can work. High-tech component sensing: through the IR chip program control, increase the sensitivity, to maintain the stability of the product. LONG BATTERY LIFE: The product is the use of CR2032 button battery (The Battery is Included), through testing, at normal operating condition, you can use 1-1.5 years, screw cap design, can replace the battery easily