Spur gear, 83-tooth, 48-pitch.Optional Traxxas spur gears allow you to increase or decrease the final drive ratio and tune for different applications.Smaller gears will increase the speed of the vehicle while larger gears will increase the torque.(for models with Torque-Control slipper clutch) Use Traxxas stock and hop-up replacement parts to get the most out of your Traxxas RTR vehicles.This product is made from high quality materials and designed for long-lasting performance.This is replacement hardware for use on Traxxas vehicles; consult your user's manual for exact parts listings.