Summary

This is a revision to the thing #353520 that BloodBlight posted. Modified the curves slightly to avoid having the filament pop off and added a bit of height to make them easier to handle. Drawing is a VariCAD file. I should add that this design was specific to 3 mm filament, not sure if it will scale for 1.75 mm. Printing was ABS plastic

Update September 7, 2014:
Printed a set of these with PLA and 40% infill. ABS is definitely the way to go; the PLA parts are too brittle to snap over the filament without snapping. ABS is much more flexible.