Re: h2testw.exe anyone??
Learned this the hard way when I bought "genuine original" ink blocks for my Xerox from a marketplace seller once, only to find out when I opened them that they were nothing of the sort, and not even the same colour as the originals. Said seller refused to refund for the open pack and Amazon were less help than might be hoped.
Regarding memory sticks and the like, the thing that annoys me is that nominal sizes vary not only between manufacturers but between batches from the same manufacturer - I run a fleet of 20-odd Raspberry Pis at work as video players and use dd (or similar) to "clone" the SD cards. The first batch of Transcend cards were slightly bigger than the second batch and both were bigger than the Sandisk cards. The Official "Samsung" Pi-logo cards were somewhere in between, but the unbranded Pi logo cards I've just bought from RS are a bit smaller.
All this means that I have to identify the smallest card to make my "original" for copying, a bit of a pain if I buy new cards that are smaller.