This variation is even more useful than my previous one as it has the clip on the filter. The clip inspired by the fantastic filament clip by intofocus I make one for each spool so I get a combined clip and filter. Quick change - so easy. You can clip the filter to the end of the filament with a small twist, You can also clip it into the spool using the clip. So its neat and tidy and holds firmly. Once again the filter section initially derived from this excellent FreeCAD version courtesy of Creative Tools. Entirely customizable. Useful Premade ones as STL also included. Very cheap to print. Uses very little material.You can't improve on the original instructions here: http://www.thingiverse.com/thing:492067/#instructions If you're making your own - remember to make the clip at least 3x the length of the filament width so it can grab on. I find 15mm quite adequate.