- Compatible with: Traxxas 1/18 TRX-4M Defender&Bronco Stock Rear Axle, and TREAL Aluinum 7075 Rear Axle. - Heavy Weight for the mini crawler, add 13g to each rear wheel and help the crawling performance. - High quality brass material - Precision CNC maching, perfect fitment. - Black coationg to prevent brass oxidation, looks better.