Front HS bulkheads enable diff height adjustment utilizing eccentric bushings. Inside front side side component gearbox, the diff height has a 2mm modification range which 2 Dot is for center diff spot. The diff height modification is a vital set-up capability which allows fast set-up adaption for either Carpet or Dirt tracks. Carpet variation operates with lower journey height and keep the drive shafts straight the differential is devote top spot. Dirt variation operates with top trip height in addition to keep consitently the drive shafts directly the differential is devote paid down destination. Fits XB4'21