:one size is enough the rear adjustable buckle design! Let you no longer worry about the size problem head circumference: 55-60 cm/21.6 inches-23.6 inches (adjustable) hat height: 10.16 cm/4 inches brim: 7 cm/2.77 inches Breathable and comfortable: 6 ventilation holes design increase the breathability of the hat. Comfortable and suitable for all-day wear the pre-curved sun visor provides better sun protection Wear it proudly! It is a patriotic hat for family friends veterans and colleagues. It is the best choice as a gift. truly outstanding american flag hats for men