Those teensy little microSD cards are just asking to get lost among the detritus of our lives, so having some way to carry them about in a slightly larger form factor is helpful. My Lozenge-sized holder is a bit more manageable to carry about, esp with the ring-hole.

You might remember my SD_Card_Six_plus_Three which holds six microSDs and three full sized SDs. It was itself a remix of card holder from @PhantomEbay.

But I've found myself mostly just swapping between two microSDs in my 3D printer, so a smaller design seemed attractive.

This one has two slots, nicely finished edges, and my patented (not really) tension-bump to ensure the card stays put in the slot nicely. It also has a chamfered key-ring hole, so you can attach it to a loop. PLUS with the small design, it prints on-edge very well, so the slots get better formed and need less clean-up after printing.

The label indent is handy for putting your contact info on, or indicating what the cards therein are related to. See my pic above for the deets.

NB: my print seems to hold the microSD cards nicely snug, yet still easily removable. There's a risk if your printer-result doesn't hold firmly. On a key-ring you may dislodge a card and lose it, so judge for yourself if it's safe to carry your data around like that. I like the loop just for hanging the thing up. :)