Terramar Thermawool CS Balaclava Constructed of Thermawool 96% mercerized supersoft merino wool, 4% spandex. Unique natural qualities include breathable moisture management and anti-microbial odor control. ClimaSense (CS) treatment is designed to respond to your body's changing conditions to keep you comfortable no matter what your activity level The CS system adapts to the skin's surface temperature, providing a warming effect when you are cold and a cooling effect when you are active, with a dynamic moisture transport system ClimaSense offers advanced odor control and uses bluesign approved, performance based technologies