We like the Skull Liner for its minimalist design that performs. It keeps sweat off your skin, traps just enough heat, and feels comfortable even during long sessions. Snug, stretch fit designed to wear under helmets, hats, or on its own. A go-to layer for anyone who needs low-profile warmth that performs in motion. Made with ultra-thin Thermax fabric for wicking warmth and flat seam construction for comfort. The 3-in-1 design works under helmets, layers easily under hats, or can be worn alone. Lightweight, 3-in-1 Thermax skull liner for wicking warmth under helmets or hats.