Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:5753537.

Added 2 small notches on the inside so Clip fits tighter around the spool and will click behind the bevelled edge of the spools. Some spools have bevelled edges inside, and some have it on the outside, this clip will click behind either edge for a better fit. And for spools without bevelled edge this enhanced clip will also be a lot tighter because of the 2 small notches inside so it wont come loose so fast.

Thanks to the original designer for sharing!