Smartwool  Men's PhD Run Ultra Light Low Cut Black/Black X-Large 55% Merino Wool, 41% Nylon, 4% Elastane Ultra Light Cushion: Minimal cushioning for maximum next-to-foot performance without added bulk. PhD = Built for Performance in the Highest Degree. 4 Degree Elite Fit System: Uses two elastics for greater stretch and recovery to keep the sock in place. ReliaWool: Patented ReliaWool technology in high impact areas provides superior durability. Men's-specific mesh ventilation zones provide additional breathability and moisture management; 200 needle construction provides highest knit density while maintaining ultra light weight. Virtually seamless toe Sock Height: Low Cut - 2.25" overall height Style: SW0SW149 Uses two elastics for greater stretch and recovery to keep the sock in place Minimal cushioning for maximum next-to-foot performance without added bulk Patented ReliaWooltechnology in high impact areas provides superior durability Men&#039;s-specific mesh ventilation zones provide additional breathability and moisture management Run-specific fit Virtually seamless toe 200 needle construction provides highest knit density while maintaining ultra light weight Sock Height: Low Cut <span class="a-text-bold">Made in USA</span>of Imported Yarn: 49% Merino Wool, 47% Nylon, 4% Elastane