How have I never discovered Sizes.com before? It's been around for 20 years and it seems to be an au­thor­i­ta­tive source on the sizes of all kinds of things: screw threads, shoe sizes, horse collars, cake pans, comas, chronolo­gies, gross national happiness, vehicle iden­ti­fi­ca­tion numbers, and much more. I discovered it when looking up penny nails.