Small: Women 5 - 8, Medium: Men 6 - 9 / Women 8 -11, Large: Men 9 - 12 Lewis N. Clark Flight Socks provide graduated leg compression and support to improve blood circulation, prevent tired, swollen legs on long flights. They aid in the prevention of Deep Vein Thrombosis (DVT). DVT is a condition in which a blood clot forms in a vein that is deep inside the body, and mainly affects the large veins in the lower leg and thigh.Intended for use with healthy legs.. Provides graduated leg compression and support to improve blood circulation and aid in the prevention of Deep VeinThrombosis (DVT). Helps prevent tired, swollen legs on long journeys. Includes one pair calf-length socks available in small, medium and large. 95% nylon, 5% spandex. Intended for use with healthy legs. Small(S Women 5 8 Medium(M) Men 6 9 / Women 8 11 Large(L) Men 9 12