The Kafka has a fixed piston filling mechanism; because of the angular barrel design, no classic externally operable rotary piston could be fitted, which is why the mechanism sits as a 'silver tube' inside. It is not a converter, that is, it cannot be removed or replaced with ink cartridges — the Kafka is therefore a pure ink filler. For filling, the mechanism is, according to the instructions, turned counter-clockwise, the nib completely dipped in ink and the mechanism turned in again; subsequent release of a few drops is not sensible given the Kafka's rather small ink volume; two drops suffice. In case of doubt, the official filling instructions in the warranty booklet should be followed.