Winter Hard Hat Liner can be used under a hard hat, safety helmet, or alone. Insulated hard hat liner is made of 100% cotton with FR (fire retardant ) treatment. The fleece interior keeps your head warm while the removable mouthpiece provides protection against cold wind. When working outside in extreme frigid cold weather protect yourself with this winter liner. The mid length winter FR hood liner is flame retardant until washed. The fleece lining, chin strap and fasteners on the insulated winter liner are flame resistant.