The SD card needs to be formatted to the primary FAT32 MBR partition type.
While the included SD card is 16 GB, Larger SD cards can also be used as long as they are properly formatted. We recommend UHS-I cards, particularly ones that are rated A1 or A2. The built-in disk-utility under Mac OS will allow you to select FAT32 for formatting. On win platforms, you will need a free external application.