This is a clip to hold a bobbin to a small Mettler thread spool. I'm not sure what other brands of spools would fit.
Just the bobbin needs to be removed- the clip can stay attached to the spool even on the sewing machine.
The ridge to snap the spool into may be too small and can get a bit messy in printing, but it works well enough for me.
Scale it up or down by a few percent to get a snug enough fit.
Modeled with Fusion 360: https://a360.co/2J2ZqzA
2 shells, I think.
Probably would work better with ABS