Outdoor Hollow Hat is a Common Outdoor Item, Usually Used for Hiking, Camping, Fishing & Other Outdoor Activities. Its Design Features a Hollow Area on the Brim of the Hat, Allowing the Head to be Properly Ventilated & Breathable During Outdoor Activities. Outdoor Hats Are Usually Made of Lightweight Materials, & Have Both Sun & Wind Protection Functions. Various Styles. Various Styles & Rich Colors to Meet the Personalized Needs of Different Users. Head Circumference 22-24.5in, & the Size Can Also be Customized According to the Customers Needs.