A pack of five marked 5ml ink sample vials for all your inking, nib-toting, aliquoting, and testing needs! Avoid contamination of your bottles by employing these hard-working sample vials as your working stock. And whatever else you may need them for. They are even great for pills in your pocket! The cap has an O-ring to help prevent leaks, and there is a frosted section for you to write on with a permanent marker. The top of the cap is flat so you can stick a round label on it for easy ink identification.