These press on top of the stock knob that came with my Makerbot Replicator 2. The internal bore allows for the knob to be installed at the end, so it's not a press fit from the top of the bore, only the last 2.5mm. The bottom of the bore has slight serrations, an attempt to match the knurl on the stock knob. The outside of the knob is a tapered serration, 20 per revolution. Doing the math, one external tooth equals approx 0.001" (screw is M3x0.5mm, so 1 turn = 1/2mm or .020") The taper is to allow for another knob piece to fit over it, with indexability. If anyone wants this, leave a comment and I'll add it. Another neat feature is that these are pressed on, but also captured, so impossible for the knobs to get bumped and fall off. Photos show (rev 1) of the design, which required press fit all the way into the bore. Rev 2 is improved, press fit only at the bottom of the bore.Print 100% infill, .1mm layer, no raft, qty 3 Remove existing knobs from under build plate Press the knobs into these printed parts Reinstall knobs