Compatible with all pens that accept a JoWo #6 screw-in housing unit.
This includes fountain pens from companies like: Edison Pens, Franklin-Christoph, Opus 88, Newton Pens, Desiderata Pens, and many, many more.
[NOT compatible with Bock nib systems, Jinhao, Nahvahlur, TWSBI, Monteverde, or Conklin]