These are #8279 differential ring and Pinion gears for the 1/10 Traxxas trx-4 scale and trail crawler. The 1.9" wheels provide a bold scale look for the trx-4 and come pre-glued and mounted to aggressive, s1-compound Canyon trail tires. Deep tread blocks flex for maximum traction on the rocks. The trail-tuned foam inserts provide realistic sidewall flex for authentic climbing action. 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.