HPI Formula Ten car owners using foam tires can now modify their cars with this Ball Differential Set that allows quick and easy tuning of the differential to track conditions for optimal handling. The set contains an aluminum axle and two lightweight aluminum hubs that are anodized in bright orange, D ring washers, ball bearings, diff grease, a 95T spur gear, and legendary tungsten carbide diff balls for the ultimate in durability and precision. The smooth and efficient diff action gives extra traction for lower lap times. This set requires the use of HPI wheels for foam tires (102915 Front and 103015 Rear).