XS: Suitable for head circumference 42-46cm S: Suitable for head circumference 46-50cm M: Suitable for head circumference 50-54cm Fit people: the UV protection hat with chin strap is suitable for most boys and girls Breathable material: the children's beach sun cap is made of polyester mainly, which is soft, lightweight, quick-drying and comfortable to wear,the inside of the cap has a breathable mesh cloth that allow heat to escape and air to flow, and it can provide you better protection from sunshine and damaging rays for face and neck Effective protection: the brim is wide enough to provide your child with good sun protection to keep the child's head, eyes, face and neck from harmful sun rays when they are outdoors, at the same time, it also has a windproof function, and the adjustable chin strap helps to fix the hat on head in the wind Wearable occasions: the wide-brimmed hat can be easily folded into a backpack or beach bag and suitable for wearing in many scenes such as beaches, playgrounds, parks, swimming pools, fishing, camping, hiking, vacations, etc. so that your child can enjoy playing and not get sunburned