Traxxas 6491X 18-t Pinion gear, 1.0 metric pitch, fits 5mm shaft (compatible with steel spur gears) 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.