The Encyclopedic Gear Set has gears from 12 to 30 and explores the theme of offset pen holes.  Each gear has an A and B version where the pen holes on one are aligned with the gear teeth and on the other they are aligned with the gaps in the gear teeth.  This allows for the creation of symmetrical designs using compound patters with ring-gear elements and gear-gear elements.

This gear set has smaller pen holes than usual.  Other than the three gears in the top right all the other gears have small pen holes (3mm) or very small pen holes (1.5 mm).  Most pens work with and fit into the small pen holes, that is what they were sized for.  The very small pen holes require pens with very pointy tips.

There are many brands of pens that will work in the very small pen holes that populate the Encyclopedic Gear Set.  The one pictured in the example photos above is a purple V5 Pilot Hi-techpoint 0.5 mm tip pen.  Art supply stores should have a wide range of types and colours available.

There are more tips about pens and paper here

Shop listing for the Encyclopedic Gear Set