This is a pen holder / servo bracket for a plotting robot. The servo can raise or lower the pen.
It is sized for a Crayola Washable pen (10.6 mm diameter) and a 9g micro servo. If you need something else, use the Open Scad file to modify it.
Full drawing robot project documented at http://www.instructables.com/id/Low-Cost-Arduino-Compatible-Drawing-Robot/
I've added one support pillar which has to be removed.