If it's been a while since you've bought portable flash memory, you might be surprised by the broad availability and affordability of high speed, high capacity microSD cards. Commonly used to expand the storage in devices ranging from smartphones to drones, microSD cards are becoming more frequently purchased than any other SD form factors, although full sized cards remain popular among digital camera owners.

Here's a quick overview of the different SD card sizes:

Standard SD cards: SD (SDSC), SDHC, SDXC, SDIO -- 32 x 24 x 2.1-1.4mm
miniSD cards: miniSD, miniSDHC, miniSDIO -- 21.5 x 20 x 1.4mm
microSD cards: microSD, microSDHC, microSDXC -- 15 x 11 x 1mm