This pack of J. Herbin Fountain Pen Ink Cartridges feature a beautiful rich blue color - Bleu Nuit and are perfect in fountain pens, rollerballs and glass pens! With their universal design, these standard short, snap-in cartridges fit almost any fountain pen or rollerball with the exceptions of Sheaffer, Parker, Lamy, A.T. Cross, Pilot/Namiki, Sailor, Platinum and Aurora. Each color comes with 6 cartridges packed securely in a cylindrical metal tin.