Diamine Imperial Purple Ink Cartridges 18/pk. Fits the standard fountain pens. This is a pack of 18 international short ink cartridges. Diamine brand ink has a long and rich history, dating back to 1864. Diamine ink is produced in the UK and is made with a gentle formula safe for all fountain pens, and has quickly become one of the most popular and sought-after brands around. We offer a wide selection of ink colors.