Amazing how warm yet so thin. I was wearing this one day when it was cold out in the morning at the beginning of the ride, around 45 degrees, held up very well. Was still wearing it when it got warm out, around 60 degrees, got incredibly sweaty and the hat absorbed all of that sweat, climbing a total of 6,000 feet that ride total, and the hat went from slightly damp to dry in 15 minutes or less. Warm and very wicking. Great product. Fits perfectly flush to your head. No bunching at all under the helmet. Totally covers ears and their lobes.