These heavyweight boot socks will handle the most extreme weather. Made with state-of-the-art construction that features densely looped Uncrushable Merino™ lambswool for all-day soft comfort, nylon-reinforced impact areas, stretch fibers from top-to-toe to provide a snug fit, and vented-rib construction for better ventilation. Flat toe seam prevents blistering; elastic arch support zone increases foot circulation. 88% merino lambswool/10% stretch nylon/2% spandex. Made in the USA. Machine wash.