The optional Level Pro self-leveling feature uses vehicle ride height sensors at each corner. The sensors contain an electrical rheostat that sends a variable chemical signal from 0-5 volts to the ECU, which then signals air valves to feed air from the onboard air reservoir to maintain-or alter-vehicle ride height as needed. The total range of adjustment is 6 inches. The sensors must be affixed to the frame with the suspension at midtravel (3 inches from full compression). The end links between the upper control arm and sensor lever are made from flexible synthetic rubber for easy mounting. The system runs at 130 to 150 psi and uses a combination of hard Teflon air feed lines and brass fittings to route the air.