Firstgear Heat Pump Vest (Black, XX-Large) Revolutionary, adjustable air chamber technology for ultimate heat retention Included Heat Pump bulb, stows in pocket and allows full adjustability of air density to customize warmth level Poly/bamboo inner lining wick moisture, dries quickly and minimizes odor retention Smooth, nylon exterior fabric for soft, no-bind, layering under any outerwear 2-way front zipper