Trekmates gore tex expedition hat black description the trekmates expedition hat is lightweight and waterproof with a gore tex membrane to allow your head to breathe whilst keeping you dry the outer shell of the expedition hat has a 50 upf rating so it will block the harmful uv rays of the sun keeping your head protected come rain or shine features waterproof windproof breathable uv protection smallmedium fits 22in 23in or 55 57cm largeexlarge fits 24in 25in or 59 61cm appr