Couple of problems here.
The Centric 12363044 is a small bolt pattern, 10" x 1.75" drum (brake diameter is measured on the inside of the drum by the way. If you look at the specs for that part number, the outside diameter is listed as 11.610", which is where I assume you got your 12" measurement). These drums are used (again, re-read the application info) on the rear of vehicles that have front drum brakes, which gives them a 4" bolt circle and 10x1.75 rear brakes.
YOUR car has front disc brakes, which means you have a 4.5" bolt circle and gives you the 10"x2.5" rear drums; Centric 12363020.
You got the brakes that you ordered, you just didn't read RA's description closely enough and ordered for the wrong brake option.
