Osprey Pens - #6 Ultra-Flex 2-Tone Nib Unit

The improved design boasts of a custom ebonite feed with tail, and a threaded housing, giving many folks the advantage of writing with ultra-flex nibs using either a pre-filled ink cartridge or with bottled ink using any generic international converter.

Typically, most suppliers in the market place sell Ultra-flex nib units with a plastic feed. Osprey is one of the handful of folks that give an ebonite feed  with an ultra-flex nib. An ebonite feed keeps up with the ink demands of a flex nib, unlike a plastic feed.