This Swimming Headband made of diving fabric material. Recommended for ages 4-9 years. Fits head size range 17"-21" If you are on the bubble for sizes it is better to go with the larger size. Velcro enclosure in the back allows for adjustability. Great for swimming, bathing, surfing, water skiing, canoeing, and kayaking. Perfect for traveling to the pool, lake or beach. Kids love them! Medium for ages 4-9 years. Large for ages 10-adult.