And it weighs only about 5 ounces! Tilley Mesh Hats are lightweight, cool and comfortable because the crowns are made of strong ?3-D? polyester mesh which blocks sunlight, but allows air to pass easily. The mesh has also been treated to provide water repellency. The 100% cotton duck brims block sunlight. Tilley Mesh Hats have been tested and certified as having a UPF 50+, the maximum UV protection rating given. The TM10 Mesh Hat is styled with the broader brim size of the Tilley T4 model. Brim Measurements: Front and Back: 3 1/2" Sides: 2 1/2"