Gear differential inside gears accuracy created from new graphite composite mixture. Includes 2 bevel gears + 4 satellite gears. Molded from an all-new unique lightweight and extra-strong graphite material provides gears an optimal stability of hardness, toughness, and freedom to provide stamina, minimal usage, 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.