This beanie has a brushed loft, and is sweat-wicking and can handle sweat continuously with the sweat. Designed to fit snugly over your head and thin so it wont get loose under a helmet. Can also be worn under a helmet; Excellent sweat absorption and evaporation; Brushed for warmth; Reduces unpleasant odor; Can be worn under a helmet; *This product (Dorout(R) beanie) uses a delicate knit fabric for both light and functionality. Repeated friction, hook hook hook and loop or branch, contact with hard objects may cause damage to the fabric.