【3.175mm】Fit 3.175mm shaft size motors, please make sure your RC motor shaft has the same diameter.
【48P】48P is the pitch of each tooth on the pinion gear. You have to make sure your spur gear and pinion gear have the same pitch, or the teeth won't mesh.
【More Funny】13T 14T 15T 16T 17T Provide the option of being able to change your gear ratio for different track conditions.