With its 4" brim to keep the sun out of your eyes, this hat also does more for your outdoor enjoyment, with odorless and invisible insect protection that is proven to repel insects such as mosquitoes, ants, ticks, chiggers, flies and midges. No Fly Zone™ has Pyrethin, a natural, World Health Organization recommended insecticide that's proven to repel insects, permanently integrated into the fabric of the hat. One size fits most.