Front HS bulkheads enable diff height modification using eccentric bushings. Inside front side side component gearbox, the diff height has a 2mm modification range which 3 Dot is for cheapest diff location. The diff height modification is a substantial set-up capability that enables fast set-up adaption for either Carpet or Dirt tracks. There's 3 different angle designs for modification of front drive train. Carpet variation runs with lower journey height and keep consitently the drive shafts straight the differential is devote top spot. Dirt variation operates with top journey height and to keep the drive shafts appropriate the differential is invest reduced destination. Fits XB4'21