Mergood TPMS Valve Stem Caps for Car/Anti-Theft Tire Pressure Monitor Sensor Indicator with Solid Brass Hardware 3 Color Eye Alert (Pack of 4) (1set) Material: Chromed Metal + Brass core + PC; Size: 0.4'' X 1.0''; 36PSI(2.4bar); Applicable to car,motorcycle,bicycle and so on. Three-color Cylinder Display: Green shows that tire pressure is normal(2.2-2.4 bar). Yellow shows that the pressure is 10% lower than standard(1.9-2.1 bar). You should inflate the tires in time. And when it is red, you need to be on guard since your tire pressure is below standard 25%(Below 1.8 bar). You must pay attention for your tires. You can make an instant judgment whether or not to inflate your tire pressure. Lets you know immediately if a tire is low and which one. Anti-tamper nut: You could tighten the caps down so no one can steal them unless they are going to have a wrench to unscrew them. Dont worry about the thief stealing it or kid playing for pranks. Brass core: It is not cheap one which is made of plastic core. The use of higher cost of copper core and gaskets, more durable. Physical detection without any energy, Put an end to chronic leaks of your tires. Although it's a bit expensive, you get what you pay. WARING: Each product is checked for hermeticity by machine prior to packaging. To prevent leakage due to incorrect installation or stem aging, please use the soapy to check the tightness after installation. Because it works in harsh environment, it is recommended to check the caps once a month and change for new one every 6 months.