"The Merino Hike+ Mountaineer Mid Calf Sock is the warmest sock in icebreaker's lineup, built with a highly dense, fully cushioned construction for the coldest hiking and mountaineering conditions. An anatomically sculpted fit with support zones at the Achilles and instep keeps that density from turning into bulk inside a boot, while a seamless toe and reinforced heel cut down on friction and pressure points through long days. The merino wool blend regulates temperature and resists odor across repeated wear in the field. What Our Gearhead® Experts Are Saying:""I wore these on a winter summit push where the wind chill dropped well below what I'd normally hike in, and my feet were the last thing I worried about all day. No hot spots either, even after ten hours in the same boots."""