Micro-Cool® process creates a wicking effect so moisture evaporates from the skin quickly, therefore providing a comfortable coolness. The mean compression for an average ankle size. Ankle, calf and length are required for proper fit: S Ankle (6.25-7.25"), Calf (10.50-13"), Length (11-15"), M Ankle (7.50-9"), Calf (11.50-14"), Length (12-17"), L Ankle (9-10"), Calf (12.50-15"), Length (13-18"), XL Ankle (10-11.25"), Calf (13.50-16"), Length (14-19"), XXL Ankle (11.25-12.50"), Calf (14.50-17"), Length (16-21"). (10-11.25"), Calf (13.50-16"), Length (14-19"), XXL Ankle (11.25-12.50"), Calf (14.50-17"), Length (16-21").