This is a Traxxas Steel Wide-Face Mod 1.0 Spur Gear - 50T [6443] 50-tooth spur gear is machined from hardened steel with extra-wide steel teeth for ultimate power handling and durability. 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.