This is a high quality hardened steel pinion gear. Fits 3.175mm shaft.
Shaft size: 3.175mm
Very Lightweight, and smooth finished. Make sure your motor is strong enough for this pinion/ have several spur size options, otherwise you might experience overheat.Nice gear, seems to work fine. The metal seems somewhat cheap, but it's meshing with a plastic spur gear, so the metal strength isn't even an issue at that point. Good gear at a great price.