I can't remember off the top of my head, but from checking Magnaflow's site, I'm pretty sure that it's the 12259...3" in/out with an offset, 18" case, 5x8 body. I got the offset as I originally had the 12249 which is center in and out, and it didn't quite fit right for my DIY exhaust. I put the offset as the inlet and the center as the outlet, which allowed the muffler to tuck up, and allowed more room for the tail pipe to clear the rear axle