For the best in breathability, comfort, insulating qualities and lightweight nothing beats US military surplus insulating layers including base layer 1 and mid layers, silkweight and some medium to heavyweight tops, shirts, drawers, long underwear bottom, pants. Great for layering in cold weather when body is highly active. These base layers are highly moisture wicking, transporting sweat away from the body. Some Base layers are FR Fire Resistant. Made mainly in earth tones like tan, desert tan, USMC coyote brown & OCP brown.