Features1、See through the transparent cap cover to check the color 2、 Green means normal air pressure, yellow means warning, and red means danger 3、 Many car parks use the 2.5bar standard to pump the car. This tire pressure cap is fully usable. 4、 This product is an auxiliary tool for measuring tire pressure. The user locks the tire pressure cap on the tire nozzle and directly visually checks the color change inside the cover to determine whether the tire tire pressure is sufficient. 5、 A 15% reduction in tire pressure will result in a 6% increase in fuel consumption and double tire wear in your car, increasing the risk of 30%. The tire pressure cap will remind you of this.SpecificationMaterial: copper, alloy, plasticSize: 11.5*23.5 (mm)Quantity: 4PCSInstructions for use:1. Normal: In the case of standard tire pressure, the transparent window should be green and the vehicle should run normally.2. Warning: The tire pressure is slightly lower than the standard by about 10%. The transparent window is yellow-green and should be inflated in time.3. Danger: The tire pressure is lower than the standard by about 25%. The transparent window should be yellowish red. It should be inspected and inflated immediately.Steps:1. Unscrew the existing bonnet2. Adjust the tire pressure to the manufacturer's recommended range. (tires must be cold)3. Screw the indicator cap onto the tire valve by hand4. Regular inspection of the cap5. If the green drop shows red, it indicates that the tire pressure is insufficient.6. Inflate the tire to the correct pressure7. Keep the bonnet clean and easy to inspect.Package List4* tire pressure cap