ClimaSense® is a propriety fabric technology formulated to adapt to an active body's changing physiology. A number of factors influence the skins surface temperature. Key among them are the outside weather conditions and the activity level. ClimaSense® is engineered to recognize an individual's need to warm up or cool down. When you are cold the fiber structure reacts by contracting to trap air and create heat. When you are hot, the fiber structure expands to allow heat and moisture vapor to escape. The result is a perfect "inner climate" balance to keep you comfortable in all conditions. ClimaSense® is proud to be bluesign® approved.