DNA Motoring HDS-GTO64V8 Stainless Steel Exhaust Header Manifold Made of high quality T-304 Stainless Steel with computerized mandrel-bends for strength and durability i.e. Maximizing smoothest high exhaust air flow rate TIG welded CNC machine flange Offers the best flow characteristics for the engine at high engine speeds Increase high flow air, instantly gain 10 -15 HP./ TQ. Inlet: 1 7/8" OD mm/ outlet: 3" OD mm/ collector outlet: 2.5" OD mm/ 16 gauge wall piping/ 10mm thick header flange