Zensah Ultra Compression Leg Sleeves give athletes a higher level of compression in the calves and shins. The Zensah Ultra Compression Leg Sleeves increase performance and decrease muscle recovery time by stimulating blood flow while stabilizing the muscles to help prevent injury. Ultra Compression Leg Sleeves are great for runners, cyclists and all other athletes. When choosing a size, calf size should be used as the primary determinant. We list height for those who do not know their calf size. Small: Calf Size 9.5" - 12.5" or 5" 3" - below Medium: Calf Size 12.5" - 15" or 5" 4" - 5" 10" Large: Calf Size 15" - Up or 5" 11" - Up.