Pinion gear is very important to transmit motor output as driving traction.
The Axon Pinion Gear is not only the shape of the gear teeth, but it also reduces the weight of the gear affected by the "sway" when the pinion gear is rotated, but also the size and depth of the hole that the motor shaft passes, and the screw position that secures the pinion gear is as close as the center of the gear and eliminates the "shaking" that occurs when fixed.
Not only is it the best match with Axon Spargears but also the best performance of any 64-pitch spargear ever
(From Amazon.co.jp)