They directly bolt on to where the original exhaust sits and do not require any further modification. Cat back exhaust systems come with exhaust pipes, muffler and exhaust tips, so you have everything you need to replace the exhaust. The cat back is the section of the exhaust that runs from the outlet of the catalytic converter to the exhaust tips. Exhaust systems that include this often feature a large pipe running from the converter to the muffler, with mandrel-bent turns and glasspacks for reduced back pressure. Your go-to spot for information on the exhaust system, as well as mufflers, catalytic converters, pipes and sensors.
Cat-back exhaust systems will include any pipes that run from the catalytic converter to the muffler, the muffler itself, any pipes that may run from the muffler to the exhaust tips, and the exhaust tips themselves. Some cat-back exhaust systems have a muffler delete, which means no muffler is included. This is typically found on vehicles that function primarily for off-road use