Our open cockpit flight cap is made from a water repellent coated polyester. It features a comfort mesh lining and strategically placed perforations to provide ventilation. Includes a FIDLOCK buckle system and snap button straps for securing communications equipment while in flight. Sizing: Medium 6 7/8 - 7 1/8 (21.25-22.5 in.) Large 7 1/4 - 7 1/2 (22.75-23.5 in.) XLarge 7 5/8 - 7 7/8 (23.75-24.875 in.)