A replacement hanging strip / insert, or whatever they are called, for hanging vertical blinds. They are approx 87mm wide which fits my 89mm/3.5 inch width blinds.
The original hangers were constantly breaking due to prolonged UV exposure, so I just replaced all of mine in one go.
They use approx 0.32m of PLA per piece.

I also have a vertical blind weight repair at https://www.thingiverse.com/thing:6619148 and a vertical blind cord weight repair at https://www.thingiverse.com/thing:6919159