HyperKewl Evaporative Cooling Caps are sure to be your best friend in the blazing summer heat! Combined cooling relief and protection from the sun Adjustable hook & loop closure with removable cooling liner 100% cotton outer with HyperKewl fabric inner, water-repellant nylon liner, and hook & loop attachments 5 - 10 hours of cooling relief per soaking 6 panel Khaki hat One Size About HyperKewl\xBB Evaporative Cooling: This simple and effective technology works by combining water with our HyperKewl\xBB Fabric to create garments that gradually release water through evaporation to keep you cool, but comfortable. Typical applications include personal cooling, outdoor safety, industrial safety, construction, emergency services, military, outdoor recreation, athletics, motorcycling and equine. HyperKewl Evaporative Cooling Baseball Cap