EnerPlex SFI-1400-BK Surfr iPhone 4/4s Case, Black Battery Case with 1400 mash capacity to increase your phones charge by 80% Slimmest and lightest battery case with integrated solar that provides robust protection for your device Charge and sync via Micro-USB with smart charge feature witch charges your phone before the case Patented CIGS technology provides the highest power density to weight ratio Energy Solar: 30 minutes of direct sun for a potential 5 minute phone call