The Ranger/BT50 centre bearing spacers are applied to the u shaped cage that holds the centre bearing into position, and effectively lowers the cage, and centre bearing, down to take the angle out of the pinion. The kit is supplied complete with 12 x 3.9mm spacer washers, to suit for the spacing requirement identified (from 3.9mm to 23.7mm), depending upon your lift. All lift kits quoted for Ford Ranger/Mazda BT50 should include a Centre Bearing Spacer Kit, because driveline vibration can be experienced even with the smallest lifts.