Simply print the 3 parts. In order to assemble it you'll need two M4 hex nuts and a M4 bolt of 50mm. Insert the bolt into the the 'adjustment screw' part and add one of the M4 nuts and tighten this. Add a little 'Loctite' to prevent the nut from loosening itself. Insert the other M4 hex nut in the outer ring and secure it in place with a drop superglue and let it dry for a couple of minutes and you're ready to go!!