You are looking at Killer B Motorsport's take on the front section of the FA20DIT powered 2015 Subaru WRX exhaust. What used to be referred to as the downpipe on EJ powered cars is now a j-pipe and intermediate pipe. Killer B Motorsport has two versions, one that retains the factory two-piece design and the other that converts it to a one-piece section. All of the Killer B 2015 WRX exhaust parts are CNC mandrel bent in the USA from 304 stainless steel and include necessary gaskets and hardware. The Killer B Motorsports J-and I-Pipes are not CARB legal and are intended for off road use only.
The two-piece kit allows you to replace one or both sections of the factory exhaust in front of the cat-back. The J-Pipe is the first section after the turbo and Killer B does away with the factory cat. You can keep the factory intermediate pipe in place with its cat and resonator or you can use Killer B's I-Pipe. The Killer B I-Pipe deletes both the second factory cat and the factory resonator. Using both components of the two-piece allows you to easily swap your I-Pipe in and out for noise and emissions reasons.
The one-piece Killer B Motorsport J/I-Pipe Combo replaces everything between the turbo and the cat back; so no cats and no resonator. It does the same thing as buying the two separate J- and I-Pipes but makes it a one-piece install. Fewer junctions. Fewer possibilities of leaks or alignment issues. If you delete one or both cats you will have to have your 2015 WRX tuned since the ECU can't compensate for the massive amount of freed up airflow. Also, keep in mind deleting both cats and the resonator will add a considerable amount of exhaust noise, so be prepared to be heard, especially if you have an aftermarket cat back exhaust on the car.