16 GB card will not work. Micro SD card cannot be SDHC which virtually all cards above 2GB are. This is an issue because most 2GB cards only have a 1.8GB volume and the OS is 1.88GB. Pretty much the only card that will work is the ATP 2GB that comes with the MC3. The ATP 2GB is available online for about $35. I am currently experimenting with other cards right now. If anyone knows a way around this please post. We have a LOT of MC3's out there.