54T motor main gear comes with 15T/17T/19T pinions and 3.175mm coupler.Three pinions is 5mm, Using the coupler can convert Three pinion apertures to 3.175mm.so this product for motors with 5mm or 3.175mm shaft diameter.3660 3670 3674 4274 4268 550 540 3650 etc series motors.54T main gear replace 3956
0.8 metric pitch; compatible with 32-pitch; pinion sinner diameter: 5.0mm/0.196inch; main motor gear dia.: 45mm/1.77inch;inner diameter: 11.9mm/0,47inch.