I'd recommend Googling how to spot a fake. I bought one on eBay that was sealed too but the speeds were a fraction of the advertised speed. I noticed some other cosmetic things and when I messaged the seller I got my $ back with no other explaination.
I'm guessing this one? - 128gb - $24.99 - 99.4% positive on 1764 feedback
I went to Best Buy after that and just forked over the money. Wasn't worth the risk.
EDIT: Not saying these are fake just saying MicroSD fakes are apparently quite common.