The 47-tooth center differential spur gear (32-pitch) is made from steel for maximum power handling and durability. The spur gear must be used with optional center differentials 10760 or 10760R. Traxxas spur gears let you fine-tune the performance of your Traxxas model. Changing gear ratios can help balance acceleration and top speed for different running conditions. Please consult your owner's manual for more information on recommended gearing options for your specific model.