That uses a modified Cross refill that I modify myself and give the customer a few spare refills, and let them know I can supply more if they run out of refills.
I have found when modifying the Cross refills that they are only half full anyways.
To extend or retract the refill, you just twist the projectile nib while holding the casing.
To change the refill, pull the projectile nib out of the casing neck and unscrew the Cross refill.
I use key ring kit finials that I have left over from making projectile key rings to fill the primer hole.
Cleaned and polished and applied 4 coats of lacquer using my "Dipping Method".
These have been great sellers to the ladies who attend the gun shows.