Router bit inserts for 20mm/MFT holes

These inserts of into a MFT holes, where the hole is 20mm and the top thickness is 18mm. I have a parametric model that goes up to 8mm, your welcome to re-mix this if you need ½ inch. I have files for metric sizes 8mm and 6mm, as well as imperial ¼ inch and 1/8 inch. 

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For printing, print it flat side on the bed, no supports, 100% infill. For safety, leave a sufficient amount of shank sticking out so you can safely pick the bit up, be safe folks!