Traxxas 8274 replaces all hollow balls on the TRX-4 Scale and Trail Crawler with lighter, smoother PTFE-coated aluminum hollow balls. 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 users manual for exact parts listings.