Super warm top! I am 6'0' 200lbs with 45-47inch chest. I bought a large and it worked well in temps 15f-30f. I used it as a base layer with a down jacket. I could have gone in much colder wether with no problems. It was too warm with a jacket at 30f. I wore it by itself many times throughout the day when it wasn't windy and was still warm. I used it while I was doing photography in yellowstone. Not itchy and wore it several days in a row. I would by again with no hesitation.