Fully sealed double-element loudspeakers - Super charged cabinet pressure converts into higher sound pressure level - Anti-skid bottom for protection and extra damping - Light weight, high stability, layering sound structured - Compatible with smart phones & tablet PCsSPECIFICATION : Power and impedance:3W4? Resonant frequency(F0):160�20% SPL:90�3dB Effective bandwidth:F0-20K HZ Maximum distortion:10% Music playing time : upto 9-12 hours Charging : DC 5V / 0.3A Charging time : 2hrs50mins / capacity : 560mAh Dimensions : 58mm x 65.3mm Weight : 110g CONCATENATION : - Support for multiple speakers play at the same time; the volume will be magnified with better experience after concatenation - With 3.5mm audio cable, support multimedia devices without Bluetooth functionality