These winter hard hat liners have a 100% quilted nylon shell, a foam middle and fleece lining. The foam and binding are fire retardant until washed. This winter hard hat liner also has two built-in pockets which hold HOT RODS® regular size warming packs. The warming packs will stay warm for 7 to 11 hours. (Sold Separately). Occunomix winter hard hat liners are manufactured with a short elastic strip in the forehead area to keep the liner snug against the face. Other winter liners do not have this feature.