Is there a UPF rating, for sun protection level?

Hi Charlie! The Proper Mesh Hat is made from 100% recycled polyester ripstop (front panel and top of bill); 83% polyester, 17% spandex warp mesh (center back panel, side panel, side crown panels); and perforated plastic (bill). There is not a UPF rating for this hat.

Is there a layer under the mesh? I'm worried that if I wear this and it starts raining, my head will get wet.

Hi Simon! There is not a layer under the mesh panels of the Propel Mesh Hat as this allows for high breathability.

Does the neon one reflect light from cars like the carbonite clothes?

Hi Kay! The Propel Mesh Hat color 041 is a part of the Run Visible Collection. The specific Nightlife Green colorway is hi-visibility, but not reflective, intended to be seen.

I love it, but I wonder if any way to readjust just a tad bigger. Any way to unhook the back of it?

Hi Juan! The band can be adjusted by repositioning the slider side-to-side along the band to alter the fit. There is no way to unhook the slider entirely without damaging the hat.

What does OSAF mean in size of a hat?

I work for Brooks. Everyone who’s responded is correct about the acronym. Additionally, I believe the diameter of this hat is adjustable from 54-57cm.