For those of you considering buying a 64gb MicroSD card with your tablet, beware of the latest crop of class10 SanDisk cards, which apparently only work with ex-fat, cannot be formatted to NTSF and only to Fat32 with a third party utility. SanDisk also reports their class 10 64gb MicroSd cards are not compatible with Android 4.0 or above, a known issue.
I can confirm that Class 6, 64gb MicroSd cards, can be easily formatted in a Windows7 computer. They work without a glitch:
Amazon.com: SanDisk 64GB Mobile Ultra MicroSDXC Class 6 Memory Card with SD Adapter - Retail Packaging: Electronics
I can confirm that the following:
SanDisk Ultra 64 GB microSDXC Class 10 UHS-1 Memory Card 30MB/s with Adapter SDSDQUA-064G-U46A:
Amazon.com: SanDisk Ultra 64 GB microSDXC Class 10 UHS-1 Memory Card 30MB/s with Adapter SDSDQUA-064G-U46A: Computers & Accessories
The above card cannot be formatted in a Windows7 computer. It is impossible to format the card to NTSF. SanDisk recommends using the following utility: HPUSBDISK.EXE, free, google it. I downloaded from Softpedia and it's quite the task to find the actual download link amidst all of the adware. I was able to successfully format the card to Fat32 for a friend who wants it for a Sandisk mp3 player, of course not compatible with ex-fat.
The Sandisk tech support guy said that their class 10 cards are not compatible with Android 4.0 or above.
This would seemingly include the following:
SanDisk 64GB Mobile Ultra MicroSDXC Class 10 UHS-1 30MB/s Memory Card with SD Adapter (NEW VERSION) - Retail Packaging with Komputerbay SDXC USB Reader
Amazon.com: SanDisk 64GB Mobile Ultra MicroSDXC Class 10 UHS-1 30MB/s Memory Card with SD Adapter (NEW VERSION) - Retail Packaging with Komputerbay SDXC USB Reader: Computers & Accessories
I ordered two but am returning both, unopened, on the advice of SanDisk and KomputerBay
The Sandisk tech support' party line is that MicroSD cards are only for phones. I don't know what they're thinking: tablets, cameras, mp3 players, mass storage... I can't understand why they would design these cards to be incompatible: ex-fat or the highway.