The 170111 is a replacement bulkhead fitting for standard ARB Air Lockers, and can be used to replace the earlier olive type fittings that are no longer available. The kit is for 5mm airline (and the 3.5mm copper pipe that comes fitted internally to the Air Locker). It is advisable to fit this kit only with the differential removed from the axle casing. Contains: O-ring compression fitting and pipe relief spring. Does not include 5mm airline. If you want to upgrade to 6mm airline the 170114 Kit can be used as a direct replacement for this 5mm kit.