World Athletic Compression Socks - Great for a marathon. One World Patterned Compression Support Socks in Medium (Sock Size 9-11, Ladies Shoe Size 5-10, Mens Shoe Size 4.5-8.5) and Large (Sock Size 10-13, Ladies Shoe Size 11-12, Mens Shoe Size 9-12.5). 87% Nylon, 13% Spandex. Knit in the USA These socks feature a graduated compression design that enhances and stimulates circulation in the lower leg, thereby increasing oxygen to the blood. Increased oxygen, means better performance and faster recovery. The benefits of wearing compression socks include - improved athletic performance; faster recovery and reduced risk of injury; improved blood circulation and oxygen delivery to cells; higher energy, stamina, and performance; cramp relief.