Rio Chiba 256 MB MP3 Player 256 MB of memory plays back over 4 hours of MP3 or 8 hours of WMA music Secure Digital card/MMC expansion slot provides up to 512 MB of additional memory Built-in FM Tuner 18-hour continuous playback using one AAA battery Compatible with computers with USB 1.1 ports running Windows 98 SE, 2000, ME, XP, Mac OS X