This is the hot racing silver 36 T spur gear for the Traxxas Revo features: conk Machined 6061-t6 aluminum hub cap and harden black steel teeth attached to hub with three screws you will receive: one hot racing silver 36T spur gear for the Revo requirements: hardened clutch bell, specifications: 36 teeth mm od mm thickness of tooth mm overall thickness comments: best use a hardened clutch bell like hot racing Srvo413 to Srvo417.