3M 40g Thinsulate insulation is one of the warmest clothing insulation on the market yet still thin enough to allow complete freedom of movement - ideal for skiing, snowboarding and any other outdoor sporting activity. Perfect for outdoor work or just for wearing on those cold winter days. Thinsulate insulation traps and holds body heat and yet allows moisture to escape. 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. Official 3M Thinsulate Insulation Thermal Hat.