Secure Digital (SD) is a flash memory card format developed by Matsushita, SanDisk, and Toshiba for use in portable devices. Standard SD cards range from 512mb to 2gb and the new higher capacity cards SDHC range from 4gb to 32gb. However many older devices are unable to read the new SDHC cards, and have compatibility issues. Consumers must check that their device is suitable.
Basic cards transfer data up to six times (6x) the data rate of the standard CD-ROM speed. High-speed cards are made with higher data transfer rates like 66x (10MB/s), and high-end cards have speeds of 150x or higher. Some digital cameras require high-speed cards (write speed) to record video smoothly or capture multiple still photographs in rapid succession.