Kamik 8mm Tall Zylex Liner - Men's Polyester Imported Comfort rated to -40F/-40C. Reinforced seams provide superior durability. Layer 1: 2mm polypropylene keeps feet dry by wicking moisture away from the foot. Layer 2: 6mm polypropylene felt blend traps body heat while wicking moisture away from the foot. Layer 3: Thermal foil provides a deflective barrier against the cold. This layer allows dampness to escape while trapping body heat and keeping it close to the foot.