Custom designed to make your hat fit snug. Perfect if you're in-between sizes! Each strip is 0.5cm/0.19in and will reduce your hat by 1 size. If you're on the border and worried that the next size up will be too loose, just add our custom Hat Filler's under the front and rear elastic sweatband. They will be out of sight while you tailor your Chiller to be the perfect fit!