Mojo Armor Battery Case for iPhone 4/4S - Gray w Ext Charger Easy Battery Change: Patent-pending design that allows for easy swapping of batteries. Modular Design: Eco-friendly with battery replacement instead of changing the entire battery bank. All other lithium ion battery case have limited charging lifespan of 300-500 cycles. Standard Battery: Modules Uses standard battery modules, allowing for compatible replacement batteries, which are readily available. Well-rounded protection: Offers heavy stress absorbing protection against knocks, drops and vibrations. Weather Sealed: Seals all ports on your handphone, protecting it from dust, sand and light splashes of water.