Rear drum questions

[Charger_70]

Hi guys , sorry for the crazy question but im rebuildin my rear drum brakes and im trying to figure out if I have 10 or 11 inch. When i measure from outer drum to outer drum i have 11 and 3/4 but when i measure inner drum to inner drum i get 10 and 3/4, i just cant remember which to go by.  Also my drum cover sticks out some kinda oval shape , most ive seen the drum cover is flat.... Is this right? Sorry for the rookie question but all help is greatly appreciated thanks.

[John_Kunkel]

Brake drums are measured by the inside diameter. Neither of those dimensions make sense.

[Charger_70]

Thanks goin by pic i have 10 inch drums.