ColumbiaPFG Mesh Ball Cap, Mountain Blue/US Flag, Large/X-Large

What size do i need for 6 7/8?

If my head is a size 7 1/8 what size do i need

I wear a size 7 1/2 what which size would fit me

Can you machine wash this hat? Got some mud on it and was wondering if I could just throw it in the washer!