Each pack of Pelikan 4001 Violet GTP/5 cartridges contains five Standard International Long cartridges. Each cartridge contains about 1.45 ml of purple colored fountain pen 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. They are generally not suitable for pocket fountain pens which often only fit one Standard International Short cartridge.
If you are using a piston filler pen or a fountain pen converter, check out our great selection of bottled inks.