Private Reserve Ink is available in 28 vibrant colors, and in both bottles andcartridges. It's a fast drying and non-clogging ink that provides excellentcoverage and a smooth flow. Neutral ph. Private Reserve cartridges come with 12 standard international cartridges in a package. Many of the fountain pens made today will accept standard international cartridges. Short standardinternational cartridges are approximately an inch and a half long.