The head circumference of this waterproof sun hat is 22.8'', which fits most people. There is an adjustable elastic drawstring on the top of the brim, which can be adjusted to a comfortable size for wearing. Soft Top Waterproof Bucket Hat is made of high quality polyester material. It is lightweight and waterproof while providing UPF 50 + sun protection. Prevents sunlight from hitting the covered areas; the waterproof fabric prevents rainwater from seeping into the inside of the hat, so you can wear it normally when you encounter rainy or wet conditions outdoors