For Mazda RX-8 Stainless Steel Turbo Downpipe - SE3P 13B-MSP R2 Made of High Quality T-304 Stainless Steel with Computerized Mandrel-Bends TIG Welded CNC Machine Flange for Strength and Durability Increase Engine Output and Efficiency; Gain 10 - 15 HPs (Approximately) Inlet: 2.75" / Outlet: 2.5" / Piping Diameter: 2.5" (Inner Diamter) Application: Please Check Part Finder on Top of The Page (Professional Installer is Highly Recommended No Instruction Included)