This sensor is the new standard for the TPMS industry. Add a 2-sensor pack to your 507 Flow-Through Tire Pressure Monitoring System, ensuring greater peace of mind and maximizing fuel savings. Ultra-lightweight and compact sensor is a perfect fit for a single axle trailer, tandem or dual wheels. Add up to 6 packs (monitor can accommodate up to 12 tow tires). Includes anti-theft installation tool No transmission when pressure is zero to extend battery life For rubber or metal valve stems | TST 507 System Sensors, 2-pack