RHX 4x 36 PSI Car Tire Pressure Monitor Valve Stem Caps Sensor Indicator 3 Color Eye 100% Brand new and high quality 4 x Tire Pressure Indicator Valve Stem Caps Material: Chromed Metal. Round Style: 36PSI. Item size: 23 x 10mm Green shows that tire pressure is normal. Yellow shows that the pressure is down about 5 pounds. Red alerts you that the pressure is down by at least 10 pounds.