Front HS bulkheads enable diff height adjustment utilizing eccentric bushings. Inside front side gearbox, the diff height has a 2mm modification range by which 3 Dot is for lowest diff place. The diff height adjustment is an important set-up capability that enables fast set-up adaption for either Carpet or Dirt tracks. You can find 3 various angle designs for modification of front drive train. Carpet edition operates with lower trip height also to keep the drive shafts straight the differential is put in top place. Dirt edition runs with top trip height and to keep the drive shafts right the differential is placed in lower position. Fits XB4'21