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Lexar unveils the world's first SD cards made of 316 stainless steel
(www.techspot.com)
This is a most excellent place for technology news and articles.
I guess if they made the chips small enough that the MicroSD body is just a shell, same thing happened with full sized SD cards (there was a time the whole space inside them was used, now it's usually a small part of the front and the rest is just the body shape for compatibility).