The Seirus Boot Masque provides extra protection against the cold in extreme conditions by providing excellent warmth and body heat retention. A durable neoprene-lined outer keeps the warmth in and wind out. With velcro the masque is adjustable to fit most boot sizes. With full coverage over the toes and top of foot, your boots will keep heat but the neoprene doesnt interfere with the boot/binding interface. loss of body heat from your boots.