Perimeter 2.0 Athletic Crew Socks. High performance athletic socks for all team sports and elite athletes. Small fits a Youth Shoe Size 2-6. Medium fits a Men's Shoe 6-9 and Women's Shoe Size 7-10. Large fits a Men's 9-12 and Women's 10-13. X-Large fits a Men's 12-15 and Women's 13-16. Fiber Contents: 75% Polypropylene, 13% Nylon, 9% Elastic, 3% Lycra Spandex.