xD Picture Card - A successor to MMC card, an xD card is considerably smaller, 20 x 25 x 1.7 mm and more robust than the MMC card. xD cards are primarily used in Olympus and Fujifilm cameras and have several subtypes. The recommended hight speed ones have to theoretical speed of 3 MB/s. Just like SD cards, xD cards too are unattractive to proffessional photographers due to their lack of speed. The storage capacity that is currently available in these cards is 2GB. Another downside is that they are not compatible with all xD compliant devices. Therefore, a comprehensive list of compatible devices is provided when you buy one.
Advantange -Comparatively compact and robust than MMC cards.