GetSprints Sweat-O-Saurus Hat Sizing is unisex. Worn once. Sprints OG hats feature an adjustable velcro closure on the back. The circumference is 22.8 inches and expands to about 24.3 inches which is a hat size 6 & 1/4 to 7 & 7/8. If you are an adult with a small dome don't hesitate to check out the kids sizes! Smoke free and shed free home. Ships fast!