UPF 50+ UV PROTECTION - it could block 97.5% or more of sun UV rays.FOLDABLE & PACKABLE - could be folded up easily into any suitcase, perfect for travel or beach Vacation.4" 10cm WIDE WIRED BRIM: large enough to supply great sun uv protection and can be fliped up.Optional CHIN STRAP: adjustable neck cord, exceedingly useful for windy daysADJUSTABLE SIZE - Medium: Best fits 55-57cm 6 3/4-7 21.6"-22.5".