QCell Sprint Motorola Photon 4G MB855 (HF5X) 3850mAh Extended Battery + FREE Battery Cover 3850mAh Extended Battery! Best Li-Ion Battery in Market! Designed in Canada! Extended Profile Design with Maximum Cell Efficiency! Comes with Free Battery Cover! DYNAStop overcharge IC stopper built in! Voltage: 3.7V / Premium Quality and Best Material used!