Rio S50 128 MB MP3 Player 128 MB of built-in memory holds up to 4 hours of your favorite music Upgradeable memory can be increased to 256 MB simply by adding a standard MMC memory card Supports MP3 and Windows Media (WMA), letting you scale the quality and playing time Integrated FM radio tuner, clock, and stopwatch Up to 35-hour battery life on 1 AA alkaline battery (or up to 20 hours with the included rechargeable battery)