ZOpid HE-ZM5800 Wireless Headphones MP3 Player with Built-in Memory and Long-lasting Rechargeable Battery Wireless MP3 Player - Behind-the-neck design for comfort and convenience 4GB built-in memory (Holds about 1000 songs - assuming each song file is about 4MB) - Use as a USB Drive to store data files Long-lasting rechargeable battery - lasts about 20 hours after a full charge Battery can be charged through computer's USB port (using included USB cable) or Optional AC Adapter (Use SKU HA-ZC5V to purchase on amazon) Use computer's File Management programs to drag and drop MP3 and WMA (non-DRM) songs to player's memory - DO NOT use song syncronization programs