Capacity

• There are no differences between the amount of memory offered by SD and microSD cards in the same category. However, there are capacity differences between the SD, SDHC and SDXC categories. For instance, SD and microSD cards provide up to 2GB of memory. SDHC and microSDHC cards offer between 2GB and 32GB of memory and SDXC and microSDXC cards offer between 32GB and 2TB. SD and microSD cards within each category are noticeably different from one another.
  
  

Measurements and Uses

• SD, SDHC and SDXC cards measure an identical 0.9 inches wide, 1.3 inches long and 0.08 inches deep and are about the size of a postage stamp. MicroSD, microSDHC and microSDXC cards are about the size of a fingernail, measuring 0.4 inches wide, 0.6 inches long and 0.04 inches deep and weigh 0.02 ounces. Standard-sized SD cards, in all varieties, are commonly used in computers and gaming consoles, which microSD cards, in each category, are mainly used in smartphones and digital cameras.
  
  

Speeds

• All SD memory cards fall into two categories: Speed Class and Ultra-high Speed Class. These classes refer to data transfer speeds in relation to video recording. SC includes four designations -- Class 2, 4, 6 and 10 -- that depend on the type of bus interface used to record video: high speed or normal. UHSC is designed for recording large-scale, high-definition video. All types of SD cards, including all SD and microSD versions, work with the SC, but only SDHC and SDXC cards, including microSDHC and microSDXC, are compatible with UHSC interfacing.
  
  

Miscellaneous

• A third subcategory of SD card -- miniSD -- is also available in each category of SD card, except for the SDXC category. MiniSD cards are about 37 percent the size of a standard-sized SD card, measuring 0.8 inches wide, 0.8 inches long and 0.06 inches deep and weighing 0.03 ounces. SD card technology is established by the SD Association, a collaborative international organization created by Panasonic, SanDisk and Toshiba in 2000. SD standards are intended to facilitate data transfer between similar devices manufactured by different companies as well as between different types of devices.