Ford 9" 31-Spline Air Locker S/N (ARBRD119)The world's premier traction aid, an ARB Air Locker keeps you moving in any conditions. A flick of the switch instantly locks the differential at any moment, and the super strong design allows activation at any speed so you can tackle the toughest terrain. With both wheels tied directly to the differential under lock, full off road traction is preserved while open differential street manners remain unchanged when the locker is disengaged. Features