When it gets dark, the LED flashes, giving the appearance of a security-equipped vehicle. The LED lights up, pauses for 3 seconds, and then lights up again, repeating this cycle. It can be used inside the car, and since it's waterproof, it can also be used on motorcycles, bicycles, and the exterior walls of houses. It's solar-powered, so there's no need to replace batteries or charge it, and it can be easily installed with the included double-sided tape. Solar charging can be done with even a little light, so you don't have to worry about the weather. The LED does not light up in bright places.