The SmartWool Men's PhD Run Graduated Compression Ultra Light Socks are the most technical wool sock with graduated compression that SmartWool has made. You get better support and a shorter recovery time. This ultra light cushioned sock protects against shock and abrasion. Features:4 Degree Elite Fit System uses two elastics for greater stretch and recovery to keep the sock in place Patented ReliaWool Technology in high impact areas provide longer lasting protection to keep feet comfortable Strategically placed mesh ventilation zones provide ventilation for temperature and moisture management 20-30 mmHg graduated compression rating 14" overall height Knit in USA of: 50% Merino Wool/45% Nylon/5% Elastane Men Compression Sock Sizing: (Shoe Size/Calf Circumference) S: 3-3.5=11-14.5" M: 6-8.5=12.5-16.5" L: 9-11.5=14.5-18"