The Outdoor Research Sombriolet Sun Hat keeps your noggin protected when you're on the water.UPF 50+ fabric protects you from intense sun, while strategically placed vents and wicking fabric in the crown keep you cool and dry.Features: Breathable Lightweight Wicking UPF 50+ Flexible Brim Piping Resists Wind Foam-Stiffened Brim Floats Wicking TransAction Headband Mesh-Lined Crown Crown Venting External Drawcord Adjustment Removable Chin Cord Avg. Weight: 3.1oz (L) Fabric: Crown: 86% nylon, 14% polyester double weave ripstop Under Brim: Supplex, 100% nylon plain weave Lining: 100% nylon mesh Measuring Guide: (Measure around head where headwear would fit comfortably) Medium: 7 1/8 = 22 1/2" Large: 7 3/8 = 23 1/4" xL: 7 5/8 = 24"