Sony NW-HD1 20 GB Network Walkman Digital Music Player 20 GB hard drive digital music player that fits comfortably into the palm of a hand or in a pocket or purse Stores up to 13,000 tracks (900 CDs) at 48 kbps when using Sony's ATRAC3plus audio format Up to 30 hours of playback with built-in rechargeable lithium-ion battery Skip Free G-Protection Technology provides quick recovery from both horizontal and vertical shock USB 2.0 cradle for PC connection and recharging