I had a slight problem with my y-axis motor being 'pulled in' and was causing belt wear and unwanted lines in my prints. You will have to drill 4 holes in the frame of the i3, so do this at your own risk. Edit 8/26/15 - Seems that AutoDesk Inventor didn't properly scale this for some reason. It needs scaled to x10 (X:67mm, Y:45mm, Z:41mm) Edit 8/29/15 - Working on the y-idler assembly now, should be up this evening! See it here! (http://www.thingiverse.com/thing:992552)Tips and tricks: Edit 8/26/15 - Seems that AutoDesk Inventor didn't properly scale this for some reason. It needs scaled to x10 (X:67mm, Y:45mm, Z:41mm) 1) Print this in the same fashion that you'd put it on the printer, the 4 motor mounting holes that are 'ears' should be the top. 2) I used ABS as it does have to bend a tad to get the motor in there. 3) I had the best luck taking the set screw and pulley off. 4) Some motors have a different dimensions so you might have to put a washer in between the motor and mount 5) One more thing, unscrewing the back bolts off the NEMA motor and using this, you will have to get 2 or 4 M3x30/35mm bolts.