Featuring all the attributes of the Medium weight USAF certified Safe to Fly cold weather sock, this heavy weight version boasts 82% Merino Wool and full cushioning, providing the ultimate in warmth, comfort and safety. Also Made in USA and 100% Berry Compliant you can count on these socks to stand up to the harshest of environments. Unisex fit URfit® System provides arch support and memory-knit construction Cushioned sole absorbs shocks and insulates Multi-filament yarn construction makes it very abrasion resistant and adds durability Smooth, flat comfort toe seam 82% Merino Wool, 11% Nylon, 5% Nanonglide® Nylon, 2% Spandex Style #6065