The AIRKÜHL^™ Cap is cut from an ultralight, quick-drying, and cooling nylon with perforated laser-cut venting. Technical construction eliminates added layers, and a foam-free ICEKÜHL sweatband reduces your skin temperature. A reflective, easily adjustable elastic backstrap creates the perfect fit and keeps you visible while UPF 50+ protects you from burning rays. This is the ultimate tech running cap for those who are relentless about the pursuit of excellence on the road less traveled.SizingS/M circumference is 54cmL/XL circumference is 58 cm