Due to batches, the original motor shaft of the 3 pro printer may not be perfectly fit for our dual . After installation, although the 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 stock motor shaft is too short to Install the . UPGRADE: Perfect replacement for 3D Printers -10/ -10S/ -10S Pro/ 3/ Tornado, etc. aluminum alloy, High quality dual extrusion, stable and durable. This Kit NOT include the and instruction manual, we need to DIY. Support: 1.75mm Filament. Some customers encountered 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 grooves, the idler drive ( not attached to the motor) is positioned on it's shaft by the motor drive dear. So, to center the idler drive properly, my suggestion for setting the unit up is as follows: 1. Assemble everything but do not lock the motor drive to the shaft. 2. Using a couple pieces of paper, shim the idler drive in the center of bracket. 3. a piece of filament in grooves and turn the motor a few turns. This should locate the motor drive in the position. 4. Lock the motor drive to the shaft, remove the paper shims, and you should be good to go. Material:Aluminum alloy colour:Photo Color Package Contents: 1 * Dual Extruder 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.