Aonijie Woolen Beanie Reversible For Running Jogging Cycling Skiing.  The primary feature of thermal hats is their outstanding ability to insulate heat. They are made from materials with high thermal properties, such as wool, fleece, or synthetic fibers like acrylic. These materials have the capacity to trap body heat close to the head, creating a warm microclimate and preventing heat from escaping. Whether you're out in a chilly wind, on a snowy day, or in freezing temperatures, thermal hats can effectively keep your head cozy and maintain your body's overall warmth.