This Ohto refill is a standard international short cartridge size for fountain pens. It fits the refill size for the Ohto Tasche and Fine fountain pens, 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.
If exposed to extremely cold weather for a long time, ink inside new cartridges is likely to freeze, expand, and push out the stopper, causing cartridges to leak.