This hat blocks 100% of sunlight and 99.9% of UV rays. It has a cooling touch function, so you can wear it coolly even on hot days. It's a FREE size with a head circumference of 56-63cm, but it can be adjusted with the Velcro strap inside. The brim is large, so it's quite deep. I used it only once, but it was too big for me, so I'm selling it.