"Fast"

This is a very fast microSD card compared to the class 4 speeds. It looks nice and it works. I'm not sure what else I can say other than that I have no problems with it and it hasn't died on my yet.It's been about 4 months at least now in my Samsung Galaxy S3. The S3 had a reputation for breaking sandisk sd cards for some reason and it's only randomly unmounted about 3 times but easily remounted with a take out and put back in with maybe a restart on the phone to refresh some apps to see it. I think this is just because the Galaxy S3 tends to get really hot right below the sd card which might damage it a bit. I don't think they put it in a good spot but that has nothing to do with the card itself so just get it if you want a nice sd card.

"Heats up"

First, it kept unmounting on the Galaxy Note 10.1I got it replaced.I used the replacement on my Galaxy S4 and it heats up my phone when charging. IT GETS VERY HOT. GS4 does not get hot with other sd cards. awaiting my second replacement.