Sizing (in head circumference)Small: 21.5"-22.5" Medium: 20.0"-23.5"Large: 23.0"-25.0"X-Large: 24.5"-26.0"Officials Wearhouse OWRP PantWaist Size : (XS 26"-30") (Small 29"-33") (Medium 32"-36") (Large 35"-39") (XL 39"-44")CCM M-150 SweaterWe suggest ordering one to two sizes larger than a normal size t-shirt that you wear.