Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:2238593.

Fit is actually a little tight for extra fine sharpies. They'll go in...but don't come out very easily.

I redid it with a pen diameter of 105 instead of 100 and they fit much better and are easily removed.

Added pens-105-18.stl - with larger holes that fit better and sized for 18 pens (because I'm horrible at counting)

Also added pens-105-16.stl - larger holes sized for 16 pens as I meant to do originally.

Customized version of http://www.thingiverse.com/thing:40406

Created with Customizer! http://www.thingiverse.com/apps/customizer/run?thing_id=40406