I ordered this in XXS for my pet with a headwidth of 9 inches and it fit like a glove. Only thing of note is some creasing/fogging behind the goggles (I'm not sure exactly what it is, they're pale marks beneath the clear plastic on the grey material) so be gentle with them. All around very happy as this specific type of hat was really hard for me to find in the right size until I stumbled across this shop!
