Specification :

High Capacity
The SD High Capacity (SDHCâ„¢) card was created to meet the market demand for higher capacity cards. SanDisk SDHC cards are fully compliant with the new SD Card Specification 2.00

Starting at 4GB, SanDisk SDHC cards is identical to the standard card in regards to performance and reliability, with much larger volume of data transfers. The SDHC cards are designed differently and use the FAT32 file systems. SDHC cards can only be recognized by SDHC host devices. Cards that are compliant with SDA Specification 2.00 will have the SDHC logo on the card

One additional description on the SDHC card is the speed class. The SDHC cards guarantee a minimum sustained data transfer rate. There are three available speed classes – Class 2, Class 4, and Class 6.
High Capacity for SD Family