Designed for extremely cold conditions the Razorback is the perfect heavy weight trekking/hiking sock. Designed specifically for extreme outdoor conditions, this multi-thickness Australian Merino Wool sock will keep you comfortable and warm in even the harshest conditions. 40% Australian Merino, 40% Acrylic,15% Polyester, 5% Elastane Superior warmth & durability Heavy weight Compression zones for a high-end fit X-tech cross-foot compression Non Slip Comfort band Seamless toe Custom cushioning SIZE GUIDE