For Honda EJ EG EK 4-1 Design Header Stainless Steel Tubular Exhaust Manifold+Piping Made of High Quality Stainless Steel Material TIG Welded CNC Machine Flange Increase High Flow Air and Maximize Performance; Instant Gain 10 to 15 Hp. / Tq. Header - O2 sensor bung insertion / Metal gasket included / Inlet: 1.75" / Outlet: 2" Test Pipe - Inlet Size: 2.25" / Outlet Size: 2.25"