Distal pen arm for EggBot

This is a customisable version of the pen holder arms used by EggBots (http://shop.evilmadscientist.com/productsmenu/51-accessories/205-distalarm).

It was designed to be a solid, one piece object without any nuts and bolts for holding it together. It actually turned out to be 2 pieces glued together, as it's easier and faster to print this way.

To allow fitting different kinds of pens (for example Sharpie Ultrafine and Sharpie Fine markers), the pen arm itself contains a hole for an pen ad