This is a high quality hardened steel pinion gear. Fits 3.175mm shaft.
Shaft size: 3.175mm
Decent gear, nice and cheap. The metal quality is questionable, but it's mating with a plastic spur gear....so who cares? It does it's job.if this is steel then it's very very soft garbage steel. I had it meshed (with proper lash) in combination with an aluminum spur and after a ten minute run the teeth on both the aluminum spur and the teeth on the pinion are gone, completely eaten. I'd expect the spur would have gotten eaten but NOT a steel pinion.It's too big to fit an SCX10 with the default spur.