To fit head (recommended): S (55-56cm), M (57-58cm), L (59-60cm), XL (61-62cm). Sewn to military defence specification and made of shrink and wrinkle resistant Cotton Ripstop fabric, this fully functional and durable Boonie Hat from MFH is fitted with four metal mesh air vents for improved air circulation and multiple attachment points for easy customization. Moreover, fully adjustable chin strap keeps the hat securely in place, while wide reinforced brim offers excellent protection against the sun. Great choice for outdoor activities, fishing, camping, hiking or travel enthusiasts.