AOLIKES 3.7V Replacement Battery 400mAh - PL 403040 for Bluetooth Headset, Mini DVR, Keychina Cam Small Camera,MP3 and More 3.7V rechargeable replacement lithium battery 400mAh , fit for MP3, MP4, Wireless Bluetooth Headset and More. Nominal voltage 3.7V, fully charged, 4.2V, 250mAh capacity of battery, Power 0.925Wh ,item model PL403040, Built-in battery protection circuit module to prevent overdischarge and short circuit of this battery. Battery size: 30 x 20 x 5 mm / 1.18 x 0.8 x 0.2 inch (L*W*T) Connector Type: 2-Pin Pitch 1.25mm; Cable Length: 2 inch, Before replacing, please contrast with the old battery and check the polarity of the battery. Red wire connection power positive " +" , Black wire connect power negative pole "-". if is a reversed, you need position of interchange wires.