Stabilo88 pen holder for ROLAND DPX-2000 pen plotter

This is an 11mm pen holder to place a Stabilo 88 (hexagonal pen) into a ROLAND DPX-2000.
Normal replacements pens are very expensive (from old stocks, no new are produced).

The outer diameter is fine, is recognized and grabbed correctly by the pen changer.
I'm still working on the inner diameter, but it is close to finished.