Golden Horizons Alum Spring Retainer Slvr Revo (2) Optional Golden Horizons Silver Aluminum Spring Retainers for the Traxxas Revo. FEATURES: Aluminum Constrution, Silver in Color, Durable. INCLUDES: (2) Spring Retainers REQUIRES: Installation SPECS: Height: 0.464 (12mm). Diameter: 0.86" (22mm)