Designed for modeling, or if you want to use filament instead of screws.If you use the 3mm filament for anything but extrusion, you need to contain it.These are snuggly fitting ends and rings to use 3mm in larger holes, or to make it lock outside of a smaller one. It shouldn’t need any real cleanup.The tapered ring is the best for holding of them all.The tapered versions don't taper very much, but may help self centering.3mmringtapered12.stl is a plate of 12. They come up best from a still heated bed, but expect to break 3 pealing them up, and 3 more pressing(hammering) filament into them. They slide down filament easily, but the ends are always flaired from the cutting, and some force will be required to get them onto it.Glue to make permanent.