... USB power or with lithium battery built-in mp3 player welcome OEM service speaker metal usb speakersParameter:1, Output power: ... ratio: more than 80dB4, Resistance: 4 ohm5, Power supply: DC5V or USB + 5V battery parameters (machine)6, Nominal voltage ... display10, Support mobile emergency charging11, Accessory : Audio cable ,USB cable, lanyard , lithium battery ,manual. Warranty Card.Payment: ...