Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Dud

I bought this for my brand new iMac when the Windows laptop I previously had died (and took its built-in card reader to the grave with it). I needed a reader that accepted multiple formats because one of my Nikons uses SDs and the other CFs. I thought SanDisk made good products ...Until I'd had this for about a month. It intermittently refused to sense the SD card, and when it did, and I copied the pictures off, then would not release it again.I now have a $20 doorstop.I haven't tried it with other types of cards, but have no reason to trust it. This is the last SanDisk card or card reader I ever buy.