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