Xtreme Free Tire Pressure Monitoring System(tpms) with 4 External Sensors and Charged by Solar Energy or USB Charging Display can be charged by solar energy or mini USB charging slot High-capacity battery, can be used normally two months The warning pressure alarm up to 51PSI. TPMS is up to 116lbs. Sleeping mode availableEasy to install Only for small car,not for vans or truck or other large car.