These are speakers that do not require an external power source as it has in-built battery, rechargeable by USB.
The speakers also come with a lanyard as well as a male to male 3.5mm audio cable and a USB cable. Any portable device, MP3 player, phone that has a 3.5mm jack can be used with the speaker.
On a full charge, speaker can last for more than 12 hours of continued playing.
