HPI Racing 87559 HD Aluminum Spur Gear Mount, Gunmetal This Heavy Duty Aluminum Spur Gear Mount is a machined alloy option part for HPI Baja 1/5th scale vehicles This is an authentic HPI bolt-in upgrade part that is precision built to the exact factory specifications for a perfect fit Heavy duty aluminum construction adds strength for resistance to melted parts and damaged gears A larger diameter ball bearing is used for improved strength and longer life