Front HS bulkheads enable diff height modification utilizing eccentric bushings. Inside front side 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 an important set-up capability allowing fast set-up adaption for either Carpet or Dirt songs. Carpet variation runs with lower journey height and keep consitently the drive shafts right the differential is devote top spot. Dirt variation operates with top trip height as well as keep consitently the drive shafts straight the differential is devote reduced destination. Fits XB4'21