Borla Universal Pro-XS Muffler Oval 3in Inlet/ 2.5in Dual Outlet Transverse Flow Notched MufflerBorla Universal Pro XS Muffler Oval 3in Inlet 2. 5in Dual Outlet Transverse Flow Notched Muffler Transverse Flow design. Transverse flow mufflers were originally designed for GM F Body Camaros and Firebirds. On these vehicles they were mounted behind the rear axle and were parallel to the axle. This muffler can also be used to create custom systems on other vehicles. Single 3" Offset Inlet Dual 2. 5" Offset Outlets. The inlet and one outlet are on one