MultiMedia Memory Flash Card (MMC) is about the size of a postage stamp: 24 mm x 32 mm x 1.4 mm. It is slightly thinner than an SD Card and can be used in most the same applications. MMC uses a 1-bit serial interface, but the newer MMC plus allows transfers of 4 or sometimes even 8 bits at a time. The slightly thinner, pin-compatible MMC cards can be used in almost any device that supports SD cards if the software/firmware on the devices support them. The MultiMedia Memory Flash Card is an ultra-small, high storage solution for MP3 music players, digital video, cellular phones, and global positioning systems (GPS). A 64MB MultiMedia Memory Card holds 64 minutes of MP3 or about 40,000 book pages.