The Tilley T5MO is made of organic, eco-friendly material. The ventilated crown helps move warm air out and cool air in, and the hat is machine washable so it will not shrink. Made of 98% cotton, 2% Spandex, this hat is only 3.5 ounces with a 2 5/8" brim at the front/back and 2 1/8" brim at the sides. An excellent hat for all outdoor activities, including golf, gardening, hiking, fishing, etc. The hat has a UPF rating of 50+, meaning it blocks 98% of UVA/UVB radiation.