Charge your smartphone anytime, anywhere with a compact, portable power bank. This portable power bank features a technologically advanced lithium polymer battery that offers exceptional performance when you need to give your smartphone an extra boost. Lithium Polymer batteries are safer and outperform their Lithium-Ion counterparts. This super-slim 11mm design has a true capacity of 4000mAh, which can effectively charge a 1400mAh mobile phone battery twice before needing to be recharged. It's suitable for smartphones and mobile phones which accept micro USB.