The Propper IHWCU (Improved Hot Weather Combat Uniform) Boonie in OCP is a lighter-weight, more breathable alternative to the standard issue boonie hat and is engineered to block sunlight and keep your head cool on hot days. Ventilation holes on the nylon/cotton ripstop crown keep the boonie hat breathable while the adjustable chin cord allows for custom fit and wearing around the neck when you want to take it off.