OHTO Fountain Pen Refill – 6pc
This Ohto refill is a standard international short cartridge size for fountain pens. It fits the refill size for the Ohto Tasche, as well as many other fountain pens. Cartridge is 1.5 inches long (39 mm). Outer dimension of the tube opening is 4 mm in diameter, inner circle opening is 3 mm in diameter, and the tail end of the cartridge is 7 mm in diameter.