This is the fleece mask preferred by high-altitude mountaineers and Antarctic scientists because it humidifies and warms winter air for comfortable breathing. A special ventilation chamber lets wearers inhale full, unhindered breaths while trapping a small amount of heated, humid exhalation. The result is a comfortable, fully oxygenated "microclimate" inside the mask with up to 80 percent humidity and temperatures 40° F to 60° F warmer than outside air. Medical studies by the American College of Sports Medicine show such a microclimate is healthier for the lungs, as excessive exposure to cold, dry air can trigger asthmatic symptoms. The medical-grade, microbe-resistant polyurethane in the chamber bonds with the humidity in the air, keeping moisture off the face and preventing fog on glasses and goggles. The mask itself is breathable, wind-resistant Polartec fleece, with hook-and-loop flaps shaped to fit comfortably over goggles and helmets. One size fits all. (2 1/2 oz.)