The Akkerman "baby long-neck" bottles have a capacity of approximately 60 ml. The faceted ink bottle is characterized by the long neck in which a glass marble is located. What makes this bottle so unique? Tilting the closed ink bottle fills the neck with ink. When upright again, the marble will fall back and prevent the ink from flowing back. This creates a reservoir with ink above the marble from which the fountain pen can easily be filled, even when the jar is almost empty.