As part of a recent effort to gather most/all my knitting and crocheting tools in one piece of furniture that I could park next to one of my knitting spots for easy, fast access, I collected my sock needles and sorted them by size in plastic tubes provided by a Scrabble friend.
My P-touch made nice labels with both US and metric sizes. To the right of the tubes you can see my traditional needle gauge and the digital caliper (less than $15 at Harbor Freight) that I use to get more accurate measurements. I've never claimed not to be obsessive about some things. Plus, I like tools.
My larger-sized DPNs are still in the roll-up I made some time ago.