Vibration dampener. Supposed to smooth things out. Might help with drone.
So... keep it? If I do that, I'll have to get a shop to weld it onto the new pipe.
I dont remember what route you decided to go with the exhaust but when I had my muffler and post muffler piping done he chopped the pipe after the dampener thing and then welded it on there. No real point in replacing the pipe prior to the dampener unless it has a hole in it.