I created this S clip to hold the cut end of filament on my 3d spools. It clips over the spool and has inner clip for filament end. Was made for Inland spools but I would imagine it would fit others. I have included the g file along with blend file if you would like to make adjustments. I was using left extruder on print in low quality since quality was not a concern. I also noticed (if you look at the last picture) the filament side of the clip slides into both the left and right inner corner notches. I printed one in each color spool I have. This not only helps to stores the clip when I load a spool, it is an easy indicator which color is loaded on each side without having to look over the back of the printer. :)
I have printed on low quality for speed since quality was not a concern. Should work with almost any settings I suppose.
Blend file included
I created in blender and have included in zip file. Scaled metric. Blend sizes are included in graphic.