Fountain pen inks are made available either in bottled or cartridge form. If the pen you own is a piston or eyedropper filler, you can use any bottled fountain pen ink, but cannot use cartridges. If the pen you own is a cartridge-converter pen, you can use either bottled or cartridge ink - but see our cartridges page for more details on which pens accept which cartridges. Still not sure which ink is right for you and your pen? Feel free to contact us at email@example.com or at (323) 655-2641.