Cat-back pipes were installed on a Sierra 2022. I installed the muffler on a Sierra 2015 and converted the pipes to a single exit on the right, and I cut the opening on the muffler because it was a double exit and converted it to a single exit. The pipes are clean, as you can see. They are 2.75 inches and come with their flanges and the opening. It just needs laser welding to the muffler.