Features an elastic slide adjustable 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. A built in sweat band wicks sweat away from your face and eyes while laser cut vents allow heat to escape keeping you cool on your workout. Sprints HyperG hats are machine washable (wash alone on cold) and hang to dry!