Preowned Sizes: One Size - up to 22" Circumference Head Age: 12 & under The STX Rival Junior Helmet is our first ever helmet made specifically for youth players. This Rival is a step up in comfort for the younger player and they will definitely notice a difference. The Rival Jr helmet has maximum size ventilation holes to increase the flow of air and keep players cool on the field. The liner of the helmet is soft foam for comfort, combined with extra soft cheek pads. Intended for players under age 9, this helmet is one size fits most and uses a sliding back piece that is adjusted with Velcro to fit to the player's head. It fits player heads up to 21 inches in circumference. To measure, just take a flexible tape measure and wrap it around the widest part of your players head from their forehead around and back again. If you don't have a flexible tape just use a piece of string, mark it, and then lay the string along a regular tape measure.