Simple cable clip

I needed a small cable clip for my [robot arm](https://www.thingiverse.com/thing:3537610). It comes in 5mm and 8mm inner diameters. If you need other sizes, you can scale the x and y dimensions it in your slicer, leave z unchanged to keep the length at 1 cm.

Sorry for the inferior print quality in the images, my extruder was clogged and I was in a rush...