The ProWikmax(R) Built In HEATR(R) Hooded Shirt, one of our more versatile products, will prepare you for temperatures reaching as low as -10 degrees Fahrenheit. HEATR(R) fabric that is body-mapped in the collar and hood, as well as ProWikMax(R) built throughout, will ensure you are warm. ProWikMax(R) will also keep you comfortable as it wicks away sweat buildup. HEATR(R) is a high-tech material developed by WSI that helps keep you up to 40% warmer than other materials on the market. Fibers that are integrated within the fabric expand and heat up as they come into contact with the skin. Since the fibers are integrated in the fabric, they will not wash out. 100% Made in USA