ThreeLeaf Rechargeable Hand Warmer 5200mAh Electronic Portable Instant Heating/USB Back-up Power Back Battery for Samsung.iPhone [SAFE FAST HEAT,SMOOTH TOUCHING] warm up double-sides rapidly in 10sec.,palm size perfect for holding, so smooth and exactly same touching feel as iPhone 6S casing. [DAYLONG WARM,2HOUR QUICK CHARGE] up to 10hours heat (auto 100~107),up to 7hours heat (medium 110~118),up to 5hours heat (high 120~130); Quick charging 2-3hours with free 2A usb line. [BACK-UP 2BATTERIES IPHONE ] full Capacity 5200mAh with max_500 recharges can give 2-4charges to Samsung/iPhone series and etc. (Free 2A usb line for Andriod mobile,and use iPhone line for iPhone charge.) [1-BUTTON CONTROL,3-HEAT ADJUSTABLE] only 1-button for power switch and one short press into Heat mode ; 3-heat optional may suit different heat demands (red 1-star: auto 100~107, red 2-star: medium 110~118, red 3-star: high 120~130) NOTE : DON'T EXPOSE THE WARMER DIRECTLY TO OUTSIDE LOW TEMPERATURE, JUST PUT IT IN GIVEN LITTLE BAG OR IN YOUR POCKET , AND THIS WILL MAINTAIN AND ENSURE THE LONG LIFETIME OF WARMER HEATING