RealWheels RW-PPK-0402 Air Guard Tire Pressure Monitor with Security Locking System, (Pack of 4) Easy to Install, Calibrate and Recalibrate For Tires with Ranges of 10 to 200-Pounds Red Strobe Indicator for Low PSI Includes Anti-Theft Security Locking System Promotes Improved Fuel Economy, Safety and Longer Tire Life