The item is a set of 4pcs car tyre pressure gauge stem caps, which fit on any standard size existing tire stem, and are specially designed to visually alert you when the tire pressure is low to help avoid premature tire wear or blowouts from under-inflated tires. You can recognize different tire pressure according to different display colors. With easy to control and install, it is really a set of wonderful car tire partner for choice. Features - 4 pieces of the car tyre pressure gauges stem caps in one set will be sold together. - - Material: durable chromed metal. - Size: about 2.3*1cm /0.91"*0.39" (L*D). - Round style: 36PSI /2. . - and Car Auto Tyre Tire Pressure Gauge Stem Sensor Indicator - Fit on any standard size existing tire stem. - Simply install on the air valve. - According the recognize color to display the pressure of the tire. - Visually alerts you when the tire pressure is low to help avoid premature tire wear or blowouts from under-inflated tires. - makes the tire of your car more safety. - Easy to control and install. Indication 1. Green shows that tire pressure is normal. 2. Yellow shows that the pressure is down about 5 pounds. 3. you that the pressure is down by at least 10 pounds. Installation 1. Determine the correct tire pressure for your tires. 2. Inflate tire to correct pressure. 3. Install this new pressure tight. 4. Simply look at the color to know if your tire is low or normal. Package list: 1 * Portable Car Auto Tyre Tire Pressure Gauge Sensor Indicator Stem - 4 pcs/set