Controlled compression assists the muscles in pushing the venous blood up the legs back toward the heart. Improved circulation reduces leg fatigue. Fashioned with controlled compression. These socks meet the needs of the active man. They provide long lasting support for the most demanding of lifestyles. 20-30 mmHg compression. Large fits 10-1/2 - 12 shoe size, 10" - 11-1/2" ankle, 12-1/2" - 18" calf cir.