The "Khaleesi Clip" was named by my wife as we are huge GOT fans (who isn't?). I didn't originally set off to design this looking like a dragon. Somewhere along the design path I noticed it was starting to look like one and I went with it.
There are three big issues I've had with any filament clip I've ever designed or downloaded in the past. The first is, the "Goldilocks" issue where the filament is either too tight, or too loose. We all know the tolerances on 3D printers are somewhat limited which makes finding the sweet spot for holding a 1.75mm hole difficult. Secondly, I use both 2.85mm and 1.75mm filaments and I wanted a 'one size fits all' clip. Lastly, I wanted to be able to install it simply without the clip falling off when it bumps into the spool next to it.
The above three things led me to a design with a tensioned clip that the filament is loaded into from the side. While the filament can be easily fed through the holes, the simplest way to insert the filament is to snap it in from the side (behind the dragons head). One hole fits 1.75mm filament and the other fits 2.85-3mm filament.
The tail of the clip is designed to hold the reel of the filament snug as well so it doesn't slide around or fall off. I have a lot of filament spools I tested it on from cardboard to super thick plastic and so far so good.
The red eye in the photo is actually printed from Prusa's MMU2 (Multi Material Unit 2). I just received it and this was my 2nd print on it. If you have a Prusa I HIGHLY recommend the MMU2 - it is amazing. If you'd like the multicolor version you can get it here: https://www.thingiverse.com/thing:3274716