Frequency on a Million Trucker Cap is 100% polyester front and 100% nylon mesh weave back. These hats super durable through regular wear and tear. They come in one size with an adjustable plastic snap closure: 22.8" (58cm). 
.: Material: 100% polyester foam front with 100% nylon mesh weave back
.: One size fits most (22.8"/58cm)
.: Adjustable plastic snap closure
.: Six row stitching on visor