10 cartridges/box.
Blue black ink is not affected due to sunlight or humidity, and it has high water resistance, which makes it ideal for permanent records.
(Quated from “Ink Type” in PLATINUM PEN CO.,LTD. web site.
*It is available only when you order a fountain pen. You cannot purchase this item alone nor with other accessories only.

Cartridges Ink【Blue Black】
$ 4