I have worn Buffalo shirts for possible 30 odd years (ex Military). They are my favourite bit of kit. My old one gave up the Ghost last year and I went straight out and bought another Special 6 shirt. I wear it everyday for walking the dogs etc, even on the coldest days I never wear more than a t shirt under it and have never been cold. Even when they get wet, they are still very warm. You can open the side zips to vent. If you sweat it wicks the sweat away and doesn't allow you to get cold. Big big fan, my go to shirt.