Sometimes things get gnarley out there. Extreme cold, snow, sleet, rain, even "snain" (that's a combo of snow and rain). When it's really wild out our Mountaineering sock doesn't back down. Extra heavy terry loop construction protects the entire foot for maximum warmth. While other extreme weather socks feel clunky ours have a smooth performance fit that keeps up with you in the worst of weather. No slipping, no bunching, no blisters. Fine gauge Merino Wool makes this a fast drying, breathable sock that stays warm in the winter and amazingly cool in the summer. And since Merino Wool is naturally antimicrobial this sock repels bacteria and odor - a great feature when you need to get an extra day (or two) out of your socks. Still made in Vermont. Guaranteed for life.