Add greater security and peace of mind while you're traveling on the road! The wireless tire air pressure sensors (caps) simply screw onto the valve stem on each working tire, replacing the dust cap to periodically monitor up to 16 wheels on your RV and tow vehicle. The sensors will monitor pressure up to 150 psi. No special tools or professional installation are required. When tire pressure is low, the monitor identifies the low tire position with a flashing light and an audible alarm to alert low pressure. The monitor is powered by a 12-volt power cord that plugs into the cigarette lighter in your vehicle. The Tire Pressure Monitor System includes a 16-wheel position RV & tow monitor, six (6) tire pressure sensors, six (6) tire pressure sensor locks, a 3-1/2" monopole antenna, power cord, visor clip suction cup and complete installation/operating instructions. Additional tire pressure sensors and locks sold separately. Note: Monitor will only display wheel positions where sensors have been installed. Monitor measures: 6-1/2"W x 3"H x 1/2"D.