Zipper allows control over how much of the head and face area are covered, reducing overheating potential. Smooth seams and soft polyester microfleece construction combine to resist wind & water penetration. Elasticized binding around face keeps balaclava close to skin, minimizing windburn and frostbite. Windflap behind zipper lessens draft, and possibility of skin or hair snags in zipper. One size fits most.