This high quality Crossfire Dual Equalizer Valve 120 PSI (set of 4) maximizes tire life by allowing pressure to move between the tires as they heat up and cool down, so they are loaded evenly, and it decreases rolling resistance for increased fuel mileage. The valves improve stability, braking, and overall safety by employing a safety feature that isolates the good tire in case of a blowout, when that occurs the internal safety valve closes with only a slight pressure loss to the good tire. It installs in minutes and since it requires little maintenance, it pays for itself in less than a year.