A small plastic adapter to put rubber feet onto a Kossel Mini/2020. The inside gets drilled out to about 3mm and threaded using a #6-32 tap. The adapters get hammered into the 5mm holes in 20x20mm extrusion. Fit's this rubber/screw foot: http://www.ebay.com/itm/221695029518 Print at 100% infill. Drill the inside to 3mm. Tap with a #6-32. Put glue on the threads and screw in the foot. Use a rubber hammer to gently push the piece into the hole.