11 Inch brakes on my 79 C-10

[punisher101st]

Hi all im having issues with my 79 C-10 rear brake shoes. I am replacing everything shoes,cylinders, brake hardware, and drums. my issue is with the replacement brake shoes, my old ones are 11"X2" which is what the factory spec is and mine are in fact physically 11"X2" but all replacement shoes from all auto parts stores Autozone, Advanced Auto, and Oriellys are Physically
12"X2" even though on their computers it says 11X2 !!! Im Stumped anyone Who can help would be greatly appreciatd.