SmartWool Men's Mountaineering Extra Heavy Crew Socks 74% Merino Wool, 25% Nylon, 1% Elastane Knit in USA SmartWool Fit System: Ankle and arch braces provide a secure fit. Extra Heavy Cushion: The ultimate in impact absorption and warmth for mountaineering expeditions. Sizing clearly indicated on the sock Flat knit toe seam Sock Height: Crew Style: SW0SW133