All I can tell you is what you see in the picture. The rears looked like they were the same size as my 07' Impala front brakes on my GTP, the rears were dual piston and I thought about pulling them off and trying them on a GP but thinking about the E-brake and the fact that I was just wanting to get out of there since it was raining I left. Don't think it will be there next time I go back, but may go this weekend. They literally looked like my front brakes. The GXP rears don't have the dual scallops on the outside where these did. The picture you show is nothing like the rears on this car. They had no ridges and dual scallop and.... Well they look exactly like 06'+ Impala fronts with a solid disc. Now this car could have been a different year, I have seen many many cars mismarked on year, model and even make. But I can tell you it was a Northstar powered Caddy
Edit: take a look at the picture ans see how far the caliper goes from front to rear, that should give you an idea of the size of the caliper. They were factory looking brakes no markings.
Jeff
