54T motor main comes with 16T/18T/20T/21T pinions and 3.175mm coupler.Four pinions is 5mm, Using the coupler can convert Four 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 replace 3956. 0.8 metric pitch; with 32-pitch; pinion sinner diameter: 5.0mm/0.196inch; main motor dia.: 45mm/1.77inch;inner diameter: 11.9mm/0,47inch. with Slash 4WD/2WD/VXL /Stampede VXL / 1/10 Summit/Trxxas 1/10 E-/T-Maxx/Jato/ VXL/Summit/T-Maxx. All metal internal gears for strength.Made of heavy duty hardened steel, long time life span. The speed depends on your ration. We four different teeth pinion to make you more choice in ration. Colour: black Material: metal Package Contents: 1 * 54T 1 * 16T Pinion 1 * 18T Pinion 1 * 20T Pinion 1 * 21T Pinion 4 * Screws Only the above package content, other products are not included. Note: Light and different displays may the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.