5-8 mm cable holder

This is a remix of [153455](https://www.thingiverse.com/thing:153455/), [1023662](https://www.thingiverse.com/thing:1023662) and [198613](https://www.thingiverse.com/thing:198613). I created a version with two different widths, 5 and 8 mm to fit the various cables in my lab. There's also [a version with 3 and 5 mm widths](https://www.thingiverse.com/thing:2754299).