Revolutionary, adjustable air chamber technology for ultimate heat retention Included Heat Pump bulb, stows in pocket and allows for adjustability of air density to customize warmth level Poly/bamboo inner lining wicks moisture, dries quickly and minimizes odor retention Smooth, nylon exterior fabric for soft, no-bind, layering under any outerwear 2-way front zipper Dual, zipper-secured, hand warmer pockets No batteries or external power source required. YOU are the heat source!