I got 2 1/2" pipes into 2 1/2" Hi flow cats. From there it's 2 1/2" pipes through (2) 2 1/2" FLow Masters over the axle with legal turn downs which 45 out back and 45 out the side with chrome tips that you can barely see on the sides. It still plenty loud and vibrates the panels in the truck. If you want it quieter, go with 3 chamber mufflers. If you turn down in front of the rear axle it will sound great but it's loud. Hope this helps.