Each tin box of Pelikan Edelstein Ruby contains six Standard International Long cartridges. Each cartridge contains about 1.45 ml of ink.
Standard International Long cartridges are 72 mm long and would fit any cartridge/converter fountain pen that can hold two Standard International Short cartridges inside its body.
If you are using a piston filler pen or a fountain pen converter, check out our great selection of bottled inks.