This hat is made of waterproof nylon and features an adjustable velcro back and fabric eyelets on the side panels. Size 1: Designed to fit kids aged 9 to 36 months Size 2: Designed to fit kids aged 3 to 5 years Size 3: Coming soon! Designed to fit kids aged 6 to 10 years Adult: One size fits most Not sure on sizing? Check out our guide. Tips for cleaning your hat can be found here.