This is a super awesome product, and was super easy to install! What this mod does is take control of the exhaust valve that is already present inside of the stock exhaust, and the company gives you a controller so you can oven and close the valve at will. Allowing the exhaust to flow the one or both of the exhaust tips. On my car I have it set up so that it's the stock muffler on the right said and a completely stripped muffler on the left (where the valve is located). So now I have a dual personality, so at one moment it's fairly tamed and quiet then when I open the valve it's almost a straight pipe with only the secondary cats remaining.