Thinsulate insulation is one of the warmest clothing insulation on the market yet still thin enough to allow complete freedom of movement. Heavy knit with Thinsulate lining. The fabric stays close to the skin allowing the hat to develop a layer of warmth between the skin and the fabric and the cuff provides a better fit. One size fits all adults and the stretchable material adds comfort & warmth. Machine Washable. Provides total protection against the elements at an affordable price.