Insul~Bright consists of hollow, polyester fibers needlepunched through a nonwoven substrate and through a reflective metalized poly film. The needled material is breathable and won't break down with washing. The hollow fibers resist conduction while the reflective metalized poly film resists radiant energy. The energy, hot or cold, is reflected back to its source. Needlepunched Insulated Lining Reflects Heat or Cold Back to the Source No Pre-wash Necessary Machine Wash and Dry Made in the U.S.A. *At least one layer of cotton batting is recommended with Insul~Bright when used as Oven Mitts or Pot Holders. Insul~Bright is heat-RESISTANT, NOT heat-proof.