The Icebreaker stuff seems to be a lot warmer than any of the Smartwool stuff. Is there a Smartwool line that's warmer than the midweight? I have never seen anything heavier than that. I have a midweight crewneck that is my very favorite piece of Smartwool, and also the Saratoga which I think is midweight, but my husband and I both have Icebreaker zip-necks that are much, much warmer than the Smartwool.