High Performance socks are superior to conventional socks because of their seamless toe, moisture wicking fibers and snug fit. 

Sizing: 
Small: Youth 2-5.5, Ladies 4-6.6
Medium: Ladies 7-9.5, Men 6-8.5 
Large: Ladies 10-12, Mens 9-12
X-Large: Mens 12.5-15.5