Earson ER-153 2.5W Wireless Portable Bluetooth Mini Stereo Speaker Compact and light-weight size,superb bass acoustic effect and 360-degree of clear sound Mini and generous design make it convenient to carry. Loudspeaker Output : 2.5W; A2DP stereo Bluetooth transmission. Impedance: 3 ; Frequency response: 80Hz-20KHz. Power supply: 3.7V 500mA rechargable battery.