The item is a set of 4 Pcs Car Tire Pressure Monitor Stem Caps, which is compatible with Cars, Trucks, Bicycles, Motorcycles, Hot Rods, Antique Cars, Classic Cars, Street Racers, etc. Visually alerts you when the tire pressure is low, to help avoid premature tire wear or blowouts from under-inflated tires. Green shows that the tire pressure is normal, Yellow shows that the tire pressure is down about 10 %, Red alerts you that the pressure is down by at least 25%. Features - Color: As shown.- Material: Chromed Metal.- Size: 2.3*1*1cm.- Determine the correct tire pressure for your tires.- Inflate tire to correct pressure.- Install This new pressure tight.- Simply look at the color to know if your tire is low or normal.- 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.Package list: 4 * Car Tire Pressure Monitor Stem Caps Sensor Indicator