UPDATE: I added an additional file for a card that holds 2 yubikeys and 2 super talent USB flash drives (which are about the same depth as a yubikey). If you have suggestions for other media let me know in a comment. I made this because I use more than one Yubikey in my day-to-day. Thought this would be an alternative to having to carry my keys around all the time. It's about the same dimensions as a typical credit card and about .5mm thicker than the YubiKey. It' seems to hold the key pretty tightly, the hole in the back is to pop them out. Later I'll try making some kind of labeling system for itI used .1mm and 50% infill. You can probably get away with .4 just fine, I think the .1 might make it a bit thinner though; not too sure how that work though honestly.