This is a replacement package of six Hot Bodies 6mm differential O-rings for the Lightning Series, as well as the D8 and D8T 1/8 scale vehicles. These O-Rings are used in the differential to seal the space around the outdrive shaft and the differential housing. These will let you seal the differential so that you can use different silicone differential oils to tune the differential action. This package includes the o-rings needed to rebuild three differentials.