This is an adjustment knob for a Daisy red dot sight, which makes it easier to dial in the azimuth and altitude adjustments. This is particularly useful if you use the sight on a telescope.
To use this, print two. Then make sure the hex nuts on the two Daisy adjustment screws are well glued onto their screws, because the knobs will attach to the hex nuts. If they aren't well glued, then glue them to the screw with superglue. Then glue on the knobs (or just press-fit). If they don't fit, increase the tolerance setting.
No supports needed.