Gear differential internal gears precision made from new graphite composite mixture. Includes 2 bevel gears + 4 satellite gears. Molded from an all-new special lightweight and extra-strong graphite material which gives the gears an optimal balance of hardness, toughness, and flexibility to provide long life, minimal wear, and minimizing breakage or teeth stripping. The lighter, graphite gears result in increased drivetrain efficiency. A Òmust haveÓ for professional racers. Fits XB4, NT1 & T4 cars.