Universal Filament clip for 1.75mm
This is a generic filament clip. Rather than clip to the reel, it clips to the other filament on the spool. Therefor there are no compatibility issues with reel thinkness, etc.
This clip is inspired by, but not actually a derivative of, GX - Filament Clip by Renae (http://www.thingiverse.com/thing:75896)
I've included the OpenSCAD file which is highly parameterized so you can easily make bigger or smaller clips for other sizes of filament (or even for other uses).