Due to batches, the original motor shaft of the 3 pro printer may not be perfectly fit for dual gear. After correct installation, although the gear on the motor shaft looks a little higher than the shaft of the motor, it will not loosen after being. Of course, you can replace the full size of 42mm high if the motor shaft is too short to Install the gear. UPGRADE: Perfect replacement for 3D Printers -10/ -10S/ -10S Pro/ 3/ Tornado, etc. aluminum alloy, High quality dual gear extrusion, stable and durable. This Kit NOT include the and instruction manual, we need to DIY. Support: 1.75mm Filament. Some customers encountered gear wear problems. The solution is: Had to change the extruder e-steps from 100 to 139 Because the filament is forced to be centered in both drive gear grooves, the idler drive gear ( not attached to the motor) is positioned on it's shaft by the motor drive dear. So, to center the idler drive gear properly, my suggestion for setting the unit up is as follows: 1. everything do not lock the motor drive gear to the shaft. 2. Using a couple pieces of paper, shim the idler drive gear in the center of bracket. 3. Clamp a piece of filament in grooves and turn the motor a few turns. This should locate the motor drive gear in the correct position. 4. Lock the motor drive gear to the shaft, remove the paper shims, and you should be . Material:Aluminum alloy colour:Photo Color Package Contents: 1 * Dual Gear Extruder Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.