This hat was designed to keep your head cool by dumping excess heat through special vents that allow hot air out, but are small enough that the sun's rays aren't an issue. Upgrade your sports gear with Isochill Armourvent stretchable baseball cap by Under Armour. This versatile cap is designed with the highest performance capabilities, including Isochill and Armourvent technologies for optimal moisture and temperature control. The stretchable construction ensures a personalized fit that does not slip or slide during your toughest workouts.