By claiming to support microSDHC (micro secure digital high capacity, SD 2.0), they are kinda required by specification to support any card that follows the microSDHC standard. I know this doesn't always happen, but that's the way it SHOULD be.
With that said, I have a 32gb class 4 card in my I2. 32gb is the limit to the microSDHC (rather, limit to SD 2.0) standard, so I suspect any microSDHC card will work.
There is no explicit support for microSDXC (micro secure digital extended capacity, SD 3.0 and 4.0, the standard that allows for up to 2tb capacity by its definition, though I think 128gb is the biggest available at the moment, and those are expensive and hard to find). Apparently the specifications allow for SDHC (and microSDHC) hosts to support SDXC cards at SDHC speeds as long as the host supports a filesystem that can format a volume larger than 32gb (FAT32 has some addressing and table allocation limits, which is why Microsoft stopped using it for primary volumes). Considering Android uses FAT32 and not exFAT (Microsoft updated version of FAT that is more efficient with larger volumes, doesn't have the low addressing limits, and optimized for flash media), I would not count on it properly supporting SDXC quite yet.
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