Originally Posted by valiantGLX
M0.3 1.0mm 9T pinion
This one seems to be as good as any, and its cheap enough, so I threw it in with my ESC order.
A long time ago, I did order a 9T pinion from HK and it didn't work (still using old pinions from burned motors). It may have been another one, but I think it was this one. Just telling you because you may want to have a "plan B", just in case.