This hat is a size small, 57. Please see company's size chart if you are unsure about the fit. https://www.gigipip.com/pages/where-to-begin I've only worn this hat a couple of times. It is so cute, but I don't find myself reaching for it enough! Aiden is a lightweight boater-style straw hat. With a UPF rating of 50+ (excellent) the tightly woven paper straw allows the right amount of sun in while a flat brim provides plenty of shade. Featuring a tonal wooden bead that adjusts the genuine leather chinstrap for the best fit no matter the weather. Paper straw. Porkpie Telescope crown. Classic crown height. Wide stiff brim. Leather chin strap with bead tie closure. Great sun protection. Dimensions - Crown: 10 cm + Brim: 9.5 cm. Adjustable inner sweat band for added custom fit. Style fits true to size.