The snug-fit Micro Dome(TM) is made with soft 100% polyester fleece for serious warmth. It weighs next to nothing, which is a big deal for those who need to count every gram. Features: - Extremely lightweight and warm - Snug fit for use under a hood or helmet - Velous Micro(TM) Fleece (100% Polyester) - Approx. Weight: 1 oz. / 29g Sizing: - Regular: Hat size 7 - 7 3/8, 21 - 22.25cm - Large: Hat size 7 1/2 - 7 7/8, 22.5 - 25cm