Tire Pressure Monitoring System. A useful thing that will always tell you that something is wrong with your tires. You can be moving on the highway, catch a self-drilling or just a sharp stone. The system will show you that the pressure in your tires is decreasing, and when it drops to critical pressure, the system will sound an alarm. The sensors are mounted on the nipples and the screen is plugged into the cigarette lighter. The size of the display is 20x17mm. Displays pressure in all 4 wheels, operates from 12V.