SD card - Wikipedia
https://en.wikipedia.org/wiki/SD_card
The SD Association defines standard speed classes for SDHC/SDXC cards indicating minimum performance (minimum serial data writing speed). Both read and write speeds must exceed the...
CARDS - What is the difference between SDHC and... | Integral Memory
https://integralmemory.com/faq/cards-what-difference-between-sdhc-and-sd-cards
SDHC cards are in the following capacities 4GB, 8GB, 16GB and 32GB. Currently, SDHC specifications allow for memory cards of a capacity between 4GB and 32GB.