Each pack of Pelikan 4001 Dark Green TP/6 cartridges contains six Standard International Short cartridges. Each cartridge contains about 0.75 ml of green colored fountain pen ink.
Standard International Short cartridges are 38 mm long and would fit a lot of different cartridge/converter fountain pens. Most notable: Pelikan, Kaweco, Faber-Castell and Graf von Faber-Castell, Visconti, Caran d’Ache, Delta, Diplomat, Montblanc, Montegrappa, and many more.