It's for the Galaxy Ace.
Transcend
or
Kingston.
both are class 4.. try class 10 or class 06 atleast if budget is not a constraint.
otherwise go with kingston
I think class doesn't matter unless you transfer a lot of files to and from your memory card to PC or the other way round. Other than that class in no way will increase or decrease the speed or response time of the device.
ofcourse class matters.. you can find the difference b/w any class 4 and class 10 card (while accessing images in gallery is the best eg to check.)
for mobile phone class 4/6 is enough..class 10 is necessary for DSLR..
if money is not a constraint go for class 10 else class 6 should be good enough..
i prefer san disk..as it is more reliable..and even at same class its performance is better than other cards...
also make sure you are getting genuine product..nowadays lot of sd cards are fake...
i bought 32 gb class 10 san disk for my tablet for Rs 1650...and 8 gb class 4 sandisk for my mobile...