The cartridge is fully compliant and suitable for my bullet Fisher space pen, she came with a small separate surely also be used for charging adapter with retractable pens of the brand ... it is not necessarily clearly reported, it is for this reason that I say and that is fine also for other users of the Fisher pens. "Space pen" ... mine at last found a second life, delivery times very good ... Now: en route to the ISS, and beyond! ;)