Outside diameter: 18cm; inner diameter: 15cm; Adjustable swim cap available for 6 months or more babies and adults. Waterproof Effect: All parts of the head are made of silica gel, elastic, soft and comfortable, and the waterproof effect is superb. Multifunction: Great for baby shampooing, shading and haircutting, it can protect child's eyes and ears from water while bathing or haircutting, makes fun experience for children, very useful and practical. Product description Color: yellow Gentle protection for baby kids and kids to keep water and shampoo out of their eyes and face, also great protection for your baby from sunscreen and haircut. All the head circumference parts are made of silica gel, elastic, soft and comfortable, and the waterproof effect is great. Outside diameter: 18cm, inside diameter: 15cm, adjustable swim cap available for 6 months or more babies and adults. Multifunction: Great for shampooing, shading and haircutting, it can protect the child's eyes and ears from water while bathing or haircutting, make a fun experience for children, very useful and practical.