My pair of Oakley Razor Blades (bought in 1989 - my shades last a while too) fit my head just fine. I guess because they are wraparounds, and a bit bendy, the width is irrelevant.
I appear to be about an 8 - I just don't wear hats (except my stretchy Subaru Impreza Drivers Club toorie) because I can never find one that fits.
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Rory
MkIIa, blue lit buttons, memory upgrade, 1Tb in Subaru Forester STi
MkII, 240Gb in Mark Lord dock
MkII, 80Gb SSD in dock