Flowmaster American Thunder Crossmember-back exhaust system for the 73-87 GM C10/C20, -+ and 3/4 ton, 2WD pickup truck is perfect for the person looking for moderate to aggressive sound levels with all of the performance benefits that you would expect from Flowmaster. This Crossmember-back DOR/DOS (Dual Out Rear, Dual Out Side) system features dual Super 44 Series mufflers, 2. 50Gg mandrel bent aluminized tubing and accommodates both dual and single exhaust crossmembers. This system is routed in a fashion that accommodates both long and short wheelbases with automatic or manual transmissions, and provides adequate clearance for substantially lowered vehicles. The exhaust system is covered by FlowmasterG??s 3 Year Limited . This system is not emissions compliant on vehicles that were originally equipped with catalytic converters. Note: This system is not designed as a direct bolt-on and will require the user to fabricate pipes to connect to manifolds or headers.