What cartridges does my fountain pen take? What cartridges does my Montblanc take?
Most European fountain pen brands use "international standard cartridges". These cartridges are also called "European cartridges" or "standard cartridges" or "universal cartridges". Short cartridges are 38 mm in length with about 0.75 ml of capacity and long cartridges are 72 mm in length with about 1.45 ml capacity.
Brands that use international standard cartridges are
Waterman (few models)
Brands that do not use international standard are
Brands that use Parker Cartridges & Converters
And some models of Lamy