This is the Weld Mfg Brushed Cotton Field Trip Hat in Eggshell.

From the manufacturer:

It’s the original hat that kickstarted our entire brand – and has become the foundation for other variations of fabrics and colors. With a 6 panel unstructured crown, the Field Trip™ is made from 100% brushed cotton twill fabric. This ultra soft hat has a timeless look that mirrors the workwear hats of years gone by, plus it includes an adjustable fabric strap with a brass metal clasp.

• Our original fit
• Crafted from 100% brushed cotton twill fabric
• Features a fabric strap with adjustable brass metal closure
  
• One size fits most (58 cm)