This is the Stock Replacement Spur Gear for the HPI Savage .21 Truck. This is the main gear that meshes with the clutchbell. Black plastic construction One 52 tooth gear One slipper pad HPIC7231 Nothing. This is a direct replacement gear. Outer diameter: 54mm (2.1") Thickness: 7mm (0.28") Pitch: 1M cmc 11/13/02 ir/kh updated tjt 042004 &