Flowmaster American Thunder Crossmember-Back Exhaust SystemThis American Thunder exhaust system comes as a complete true dual Crossmember Back exhaust for your 1968 1972 GM A body with a V8 engine. These dual exhaust systems feature 2. 50 inch mandrel bent stainless steel tubing for maximum performance, includes a built in H pipe balance tube flowing into a pair of large case Super 40 mufflers that deliver an aggressive interior and exterior tone and are suited to the enthusiast who wants their performance to