The broad-brimmed Outdoor Research Helios Sun Hat protects you from intense sun with a UPF 50+ rating. The headband moves moisture away from your brow, and the brim offers an oasis of shade. The drawcord adjustment keeps it snug on long trails. Features Breathable Lightweight Wicking UPF 50+ Foam-Stiffened Brim Floats Wicking TransAction Headband External Drawcord Adjustment Removable Chin Cord Avg. Weight: 2.3oz Fabric: Crown: 86% nylon, 14% polyester double weave ripstop Under Brim: Supplex, 100% nylon plain weave Measuring Guide: (Measure around head where headwear would fit comfortably) Small: 6 7/8 = 21 5/8" Medium: 7 1/8 = 22 1/2" Large: 7 3/8 = 23 1/4"