2004-2007 Cadillac CTSV headers. 1 3/4" primary tubes with 3" od collectors-headers only. Long tube design makes great power and mid range torque. 3/8" s/s CNC laser cut flanges are port matched to the cylinder head for optimal flow and maxium performance. Fits excellent with Stainless Works headers but will require some cutting, welding, and fabricating to connect to the stock or aftermarket exhaust systems. Tested at Strope Speed Shop, our stock 2005 CTS-V with Stainless Works headers and catback with a tune made 53 HP and 47 TQ to the wheels over stock!!!!