There are four standards for capacity:

SD SD standard – Up to 2GB SD memory card using FAT 12 and 16 file systems
SDHC SDHC standard – over 2GB-32GB SDHC memory card using FAT32 file system
SDXC SDXC standard – over 32GB-2TB SDXC memory card using exFAT file system
SDUC SDUC standard – over 2TB-128TB SDUC memory card using exFAT file system
SD Standard SDHC Standard SDXC Standard SDUC Standard
Capacity up to 2GB more than 2GB

up to 32GB

more than 32GB

up to 2TB

more than 2TB

up to 128TB

File System FAT 12, 16 FAT 32 exFAT exFAT
SD Logo SD SDHC SDXC SDUC
Form Factor Size SD 32 x 24 x 2.1 mm
microSD 11 x 15 x 1.0 mm

Speed Classes
NS mode C2, C4, C6
HS mode C2, C4, C6, C10,

V6, V10

UHS-I

mode

C2, C4, C6, C10

U1, U3

V6, V10, V30

UHS-II

mode

C4, C6, C10

U1, U3

V6, V10, V30, V60, V90

UHS-III

mode

C4, C6, C10

U1, U3

V6, V10, V30, V60, V90