This is the optional JConcepts 48P 81T Silent Spur Gear for the Associated B4.1, T4.1, B44.1 and SC10 Vehicles. FEATURES: Precision machined composite material for a more consistent gear mesh, more precise adjustment and quieter operation Pattern vented area INCLUDES: JConcepts 48P 81T Silent Spur Gear jxs 01/17/12 ir/jxs