To measure for a hat, circle the crown of the head with string or dental floss, above the eyebrows and ears. Measure the length of string on a ruler and compare to the size ranges listed in the hat description—there’s your size! Many, but not all, of our hats feature an adjustable sizing system. When you receive your hat, loosen or tighten the adjustable sizing system (if available) as necessary for your custom fit. Wearing the hat slightly above eyebrows and ears will allow clear front and peripheral vision.