The Secure Digital (SD) Memory Card is the fastest growing memory card format in the digital storage industry. Originally based on the MultiMediaCard format, Secure Digital was designed by a consortium of Matsushita Electric (Panasonic), SanDisk and Toshiba, to facilitate the secure exchange of content between a card and its host devices. SD cards can control the use of a card's content as subscribed by Digital Rights Management (DRM). Although DRM is not frequently used, SD audio devices do require audio encryption, and therefore may not allow other types of files, such as picture files, to be written on the same card. SD Cards are slightly thicker than MMC cards (32mm x 24mm x 2.1mm), with nine gold slide contacts (compared to seven on MultiMediaCards) and a write/protect switch on the card, enabling the user to lock the digital content so it cannot be erased or overwritten. SD cards are also faster than MMC in terms of read/write speeds, another factor that has added to its popularity. MultiMediaCards can be used in Secure Digital slots, but SD cards are too thick for use in MMC slots. The cards are currently available in sizes up to and including 2GB.