This is an elegant way to carry around a spare ink cartridge or two. Fitted with either a Large LobsterClaw clasp or a small Carabiner style clasp, you should be able to clip this little stash to just about anything. From a Backpack to your pants loop, you should always have some spare ink with you.
It has been designed to carry two Short International Standard cartridges or one Long International Standard. While I have not extensively tested it, I believe it should fit at least one of your favourite proprietary cartridges.
The interior dimensions vary between designs, they are handmade after all. The holding capacity will be at least 8X80mm.