I purchased the SanDisk Ultra 128GB MicroSDXC Class 10 UHS Memory Card Speed Up To 30MB/s With Adapter off Amazon. I took my Sandisk 64gb micro SD and the 128gb and attached both to a desktop PC, transferred all the files off my 64 to the 128, and placed the 128 in my s3. It seems to be working just fine. The system reports the proper amount of original space and leftover space. It's been 3 days and I'm happy so far. I got mine here: http://www.amazon.com/gp/product/B00IIJ6W4S/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1 . It's currently $119 plus shipping, you may be able to find it for less somewhere else but that's where I bought mine.