Front HS bulkheads enable diff height adjustment using eccentric bushings. Inside front side gearbox, the diff height has a 2mm modification range where 3 Dot is for lowest diff destination. The diff height adjustment is an important set-up ability 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 version operates with lower trip height and also to keep consitently the drive shafts directly the differential is devote top spot. Dirt version operates with top journey height and also to keep consitently the drive shafts right the differential is put in reduced position. Fits XB4'21