Popular hamburger mini TF card speaker, high-fidelity, low-power; for MP3,notebook,cellphone;aluminum shape;last for 4 hours Product Features:1. ... Capacity:550 mAhDistortion :< 0.5%Charge Voltage:5V+0.5VOperating System:Microsoft Windows Vista, XP sp2 Mac Os 10xCertificates:CE & ... *41cm*40cm 100pcs/cn(Big cube packing) Popular hamburger mini TF card speaker for mobile,laptop,iphone, with bluetooth