It has a fast heating technology to keep your body warm. Dartwood Rechargeable Hand Warmers can also function as a power bank for emergency battery charging which makes it a perfect gift in cold winter. These hand warmers give you up to 7 hours of warmth in one charge. It improves blood flow and circulation, soothing discomfort, and increases muscle flexibility. These hand warmers give you up to 7 hours of warmth in one charge. It improves blood flow and circulation, soothing discomfort, and increases muscle flexibility. Unlike the cold metal surface, this hand warmer is made of high-grade aluminium and ABS plastic, giving a glossy and warm feel and touch. Keep Yourself Warm. 5200mAh power bank compatible with Android phones and iPhones. Fits into your hand. Up to 7 hours of warmth. Lightweight: 135g. 3 Heal Levels up to 131F. Best winter gift for your love ones.