Replacement for over charged internal batteries or dying battery cells. Prolong the usage life with a replacement battery. Including tools needed to open the phone and replace battery. Designed for iPhone 5. 3.8V built-in Li-ion battery. 1440mAh high capacity battery cell, ensure longer battery life (more than 500 cycles) and high-speed, efficient charging. Over charge protection, over-discharge protection. Short circuit protection, anti-explosion protection.