Using fabric technology developed by Nasa for spacesuits, we have produced a beanie that can be used for daily and sporting activities in all environments. One size fits most. The Outlast beanie from Charm maintains the temperature against you skin at 87 to 91 degrees , whether you be in the heat of the direct sun in summer or in the middle of winter. By Storing and then releasing the heat as a reaction to the surrounding temperature, Outlast fabric keeps you more comfortable. The beanie is even effective when worn under a helmet during cycling, motorbiking or other sports.