From the album: Mercian’s pens
The front of the point-of-sale package in which my Pilot Plumix ‘F’ arrived.
My pen is a European-market version, so takes ‘short international cartridges’.
Caveat lector:
A long’ ‘international’ cartridge just about fits in to this pen, but if one unscrews the barrel from the pen, doing so pulls the cartridge off the feed-nipple!
At least, it does that to the (already-empty) Pelikan GTP5 cartridge that I tried in the pen.
I do not know whether it would also do that to e.g. a long cartridge made by Waterman.