This sprocket is referred to often and referenced to the Rapman Wiki. I put a copy up here in case something happens to the Wiki and the file goes away. It replaces part 10014 and the two stars above/below it. File's origin is here: http://www.bitsfrombytes.com/wiki/index.php?title=Spare_partsThe grub screw fell out of my acrylic Z drive sprocket. When reinstalling it, I heard a click... and noticed that the belt would lift up on the sprocket then fall down into the teeth. Tightening the grub screw expanded the acrylic so it wasn't working with the belt properly. I promptly printed the ABS sprocket from this file and am using it now. Double check the height of the tensioner bearing. I noticed that mine was offset a bit as assembled according to the instructions. Once I pressed the new sprocket on the Z stepper, I shimmed the bearing and its washers down to line up with the teeth of the sprocket.