Military Thermals Polypropylene Thermal Balaclava 100% Polypropylene Polypropylene clothing should be washed in cold or warm water and hang to dry, or VERY LOW dryer heat. 100% MADE WITH PRIDE IN THE USA! Very soft and breathable Polypropylene does not absorb moisture from your skin, but transfers the moisture to outer layers. Unique moisture transfer abilities of the fabric keeps your clothing warm and dry. Polypropylene has the lowest body heat conductivity of any fabric available  including silk, polyester and wool.