tftdrd60 wrote:32.0mm x 24.0mm for the model B and 11.0mm x 15.0mm for the b+
I WAS refering to the capacity of the SD drive not the physical size!

I know, I was trying to say that the capacity is irrelevant[1]. All cards are supposed to use the same protocol[2]. Just avoid class 10 cards[3] for now.
Pedant proofing the above:
[1] The sd spec has some things to say about what the filesystem should be, but that's irrelevant.
[2] Yes, there are different bus types.
[3] I'm sure many people use class 10 cards without any problems.