Prusa i3 Filament Guide Clip

First, I replaced the shipped spool holder on my Prusa I3 with this one:
[Spool Holder for Prusa i3 MK2 - Hex Design ](http://www.thingiverse.com/thing:1832235)

To prevent pulling the filament sideways off the spool, I needed a filament guide. I made the Filament Guide ClipOn by Area51 first, but after some usage, I improved a few things:

The loop was originally with a parallel gap between both halves, meant to close when put into the holder. But that cannot work this way because it then