Hyundai Genesis Coupe 3.8L V6 Stainless Steel Downpipes Made from High Quality T-304 Stainless Steel TIG Welded CNC Machined Flanges Direct Bolt-On Installation; Requires No Modification Increase High Flow Air, Instantly Gain 10 -15 HP. / TQ. Piping Diameter: 2.5" with Flex Pipe Insertion for Extra Strength Includes O2 Sensor Bung Insertions Bolts, Gaskets, & Hardware Included As Shown In Pictures NOTES: No Installation Guides Are Included, We Highly Recommend To Seek Professional Installation