The Multi Media Card or MMC is the smallest removable flash memory designed specifically for digital applications, such as MP3 music players, digital video cameras, PDAs, mobile phones, voice recorder and digital still cameras. The Multi Media Card has a wide variety of uses in some of the most exciting products on the market today.
New RS-MMC (Reduced Size MultiMediaCard) has the same width but almost half the length of existing MMC cards, RS-MMC cards will be 24 x 18 x 1.4 mm. It's clear that this new reduced size format is aimed primarily at the mobile phone / PDA market but it would also offer digital camera manufacturers the opportunity to build even smaller digital cameras.
A reduced size card can be used in a full size MultiMediaCard with a simple mechanical expander that will make the card "regain" a full size format.