1. Storage Capacity : This indicates the storage spaces that a certain card can hold.
2. Write-protect Logo : In order to use the SD card, make sure that the tiny lever is at the top of the symbol which signifies that it’s unlocked and is not write-protected.
3. Read Speed : Is the maximum read speed that the SD card can be read based on the manufacturer’s internal testing.
4. Format: There are currently three SD formats – Secure Digital Standard Capacity (SDSC or just SD) that uses FAT 12/16 file systems and tops out at 2GB, Secure Digital High Capacity (SDHC) which makes use of FAT32 file system and supports up to 32GB memories, and Secure Digital Extreme Capacity (SDXC) that utilizes exFAT format and can go as high as 2TB.
5. Speed Class: There are currently four (4) Speed Classes that is defined by the SD Association – Class 2 (2MB/s , min) , Class 4 (4 MB/s , min) , Class 6 (6 MB/s, min) , and Class 10 (10 MB/s, min).
6. UHS Class: There are two UHS classes ; UHS Speed Class 1 (U1) and UHS Speed Class 3 (U3). Similar to Speed Class, the maximum speed of a UHS SD cards can only be achieved if the host device supports the UHS speed class. If it’s a non-UHS device, it will default back to Speed Class which explains why some SDHC and SDXC bears both speed class and UHS speed class markings on it.