Wear Winter Liners alone or under hard hats to protect against extreme cold and wind while working outdoors. Back reflective strip and suspension straps attach liner to hard hat. Come with 2 pockets on either side to hold companion Warming Packs, which heat up to 144 and offer 10 hrs. of warmth. Warming Packs come in packages of 5 pairs. Elastic strip along forehead and hook and loop closures around neck allow snug fit to prevent wind from entering. Sherpa Liner (shown) features cotton shell with sherpa lining. Comes in medium and shoulder lengths. Also find heavyweight polyester All Fleece and flannel, fleece, or layered nylon All-Purpose Liners. Knitted Tube style fits over hard hat.