Gear differential interior gears precision made from new graphite composite mixture. Includes 2 bevel gears + 4 satellite gears. Molded from an all-new unique lightweight and extra-strong graphite material gives the gears an optimal stability of hardness, toughness, and freedom to supply stamina, minimal use, and minimizing breakage or teeth stripping. The lighter, graphite gears end up in increased drivetrain efficiency. A must have for expert racers. Fits XB4, NT1 & T3 automobiles.