The N-Ferno 6813 Winter Skull Cap Helmet Liner is lightweight and breathable for warm comfort in mild to cold conditions. Designed to fully cover the head and ears, this low-bulk thermal skull cap can be comfortably worn on its own or beneath helmets and hard hats. With a brushed thermal interior and durable pill-resistant exterior, this winter beanie is made for long-lasting wear. This winter helmet liner is ideal for those working in construction, transportation, warehousing, refrigerated areas and more. Can also be worn for weekend activities such as hunting, climbing, running, cycling and skating.