What size pipe is factory Y on a 6.2?

I was going to order some ball/flange collectors to mate my pacesetter 3" collector headers to the factory Y on a 2010 6.2 Sierra. I realize there will be some cutting and welding, just trying to figure out if I needed the 3in or 2.5in?

Thanks

Interested in trading your stock y pipe for my pacesetter y? It is already modded to fit the 6l80 and bolt up to the stock exhaust.