What is the purpose of this fin like structure on these pens (uniball eye), it seems to fill up when the ink gets used, does it serve some practical or is it
Unique Fountain Pens | JetPens
Fountain Pen Manual
How the capillarity and ink-air flow govern the performance of a fountain pen - ScienceDirect
Different Types Of Fountain Pen Feeds | EndlessPens | EndlessPens
Fountain Pens – Loft Pens
BEX6E Bexley Replacement Feed and Housing, Black Ebonite – Flexible Nib Factory LLC
How the capillarity and ink-air flow govern the performance of a fountain pen - ScienceDirect
Discover the Hidden Parts of a Fountain Pen – stilform GmbH
Fountain Pen Basics: What is a Fountain Pen Feed? – Writer's Bloc Blog
Zen and the Art of Fountain Pen Maintenance — The Pen Addict
fluid dynamics - Why does a fountain pen soak ink automatically at times? - Physics Stack Exchange