This is a portable speaker, it's built-in digital amplifier and 2x2w speaker to make you enjoy high quality stereo sound. and built in A-grade batteries lithium can play longer . on the left side of speaker is power on/off and aux in to make you operation easier, you can play music through the aux in such as iphone,mp3,mp4 ipod...
specifications:
Power：USB/Lithium battery
 

Output：RMS 2W*2 THD+N1%
 

Frequency：120Hz~20KHz(Hz)
 

SNR：>90db
 

Response sensltivity：90db
 

Impedance：4HM(Ω)
 

Power input：USB DC 5V
 

Speaker unit：36mm
 

Case material：Pure ABS
 

Dimensions：105mm*45mm*22mm