1.this player can work without any external speakers, so it is portable. 2.this player has ternary jack for charging,data exchange & built-in power switch 3.music format: MP1 / MP2 / MP3 / WMA / WAV /ASF /WMV 4.port mode: USB 2.0 5.EQ mode: pop / classic / soft / jazz / dbb / rock / normal 6.playing time: continuously playing time for 350-400 minutes after fully charged 7.battery voltage: 3.7 V rechargeable Li battery 8.output power:55mw 9.headphone output power:5mw 10.requency response: 20Hz-20KHz 11.battery charge time : about 3 hours 12.working current: 35-40 MA 13.info/noiseratio:86dB 14:Color:silver 15: this product 's main body is headphone, and built-in mp3 and Li battery.