Mojo Vogue Battery Case for iPhone 4/4S - White 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 light stress absorbing protection against knocks, drops and vibrations. Fast Charge: Halves your charging time (compared to a std 500 mAh USB output power).