BREATHABLE & COOL - Lightweight mesh panels for better ventilation and keep you dry and comfortable. Solid, durable mesh vents prevent your head from feeling stuffy. ADJUSTABLE & QUICK DRYING - The back is easy to adjust. The adjustable, stretchy strap at the back does a great job of taking up any slack so the hat fits all head sizes. You won't feel too tight or too loose. It can dry very quickly. PORTABLE & LIGHTWEIGHT - The crown of the hat is unstructured, so it can be folded and fit into any bag. Combined with airy, lightweight fabric, this cooling hat can give you a light feeling. And you can take it with you everywhere and it doesn't take up too much space, giving you a lot of convenience during use. SIZE GUIDE - For head circumference: The back is easy to adjust. PERFECT FOR WATER SPORTS - The material does not get wet like a regular cap. It will not make you feel uncomfortable if it gets wet. Perfect for runners, golfers, tennis players, golf, tennis ball, fishing and all indoor or outdoor activities.