6 Tire Cap Sensor RV/Truck Tire Pressure Monitoring System (TPMS) The external cap sensor with replaceable battery can be secured to prevent loss or theft Portable monitor has rechargeable battery and monitors tire pressure 0-199 PSI & temperature Monitor tires 24/7: low/high pressure, high temperature, and slow leaks. Monitor warning thresholds are user adjustable; low pressure alert level is per axle adjustable. Tire sensor signals have excellent range and not require signal booster for most vehicles