SD cards are 24mm x 32mm in size and have high transfer rates at low power consumption which makes them popular for battery powered devices.

SD cards are an improvement of the MultiMediaCard (MMC) and have in turn been improved as products termed SDHC (high capacity) and SDXC (extended capacity).

Smaller versions known as the miniSD card (20mm x 12.5mm) and microSD card (11mm x 15mm) also exist.

See also:

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