The N-Ferno 6877 Winter Hard Hat Liner has three layers of insulation with an FR modacrylic/cotton blend shell, a foam mid-layer and a comfortable polyester fleece lining for extreme warmth. This lightweight thermal liner is shoulder-length to keep head, ears and neck covered and fits comfortably under helmets or hard hats without feeling too bulky. Please note this garment is not entirely fire-resistant. The fire-resistant outer shell is made 60% modacrylic cotton and 40% cotton twill blend to stand up to tough environments with inherent flame resistance and self-extinguishing properties. Foam insulation provides an additional layer of thermal protection for extremely cold environments. The 100% polyester fleece lining is soft to the touch for a comfortable all-day fit. There are four hook and loop straps on the exterior of the liner designed to securely attach to the interior of a hard hat for versatile protection in extreme work environments.