Teflon-cutting guide

I needed a simple guide that would allow me to cleanly recut one of the two ends of the PTFE tube installed on my 3D printer. The guide fits any 4 millimeters diameter teflon tube.

The [PrototypeMe's version](http://www.thingiverse.com/thing:686792) was overkill for my needs so I decided to remove the extra parts of the original piece with MeshMixer.

*Oh, and I know my cutter is rusted as hell. I definitely should replace it. :-D*