I noticed this a couple of months ago - the Altoid sour metal cases are a perfect size for UMDs. You can pick them up next to the gum and mints at any grocery store - they taste good too! You can fit three UMDs into each one. I also keep my extra memory stick and cleaning cloth inside. They are hard metal so you donít have to worry about your UMDs being crushed; this is a great way to protect your valuable UMDs without paying for expensive protective cases!