Dress Up AmericaTop Hats for Kids - ian Hat - Unisex Formal Tuxedo Hat - Available in Red And Silver

What size does this hat fit? I have a 6 month old with an 18 inch head circumference. Will it fit him? Thanks.

My 10 year old loves this hat but it’s become pretty stinky from sweat! How can I wash it?

Is the circumference 19" or no?