The push-knob filler was MONTBLANC's own development. The blind cap is screwed back to a stop (1) and stays connected to the barrel – so it can't get lost. It is then depressed and bents a flexible metal band (2) in the barrel, that compresses the rubber sac (3) inside. Releasing the blind cap straightens the steel band, the sac takes up its former shape and fills with ink.