Sheaffer's push-in piston converter, which replaces a cartridge and lets you fill the pen straight from a bottle of Skrip. The smoke-tinted barrel means you can see at a glance how much ink is left, and the screw-action piston draws a full fill in one turn.
It fits every Sheaffer fountain pen except the VFM, which uses standard international fittings and needs an international converter instead.
The obvious next purchase after a bottle of ink.
