They are on the website for hop-up racing. Major $$$, but I'll pay if the sound is right.......not loud.

 

I love NISMO parts. I could not justify paying that much for high flow cats. I figured I would settle with high quality stainless steel cats. I chose Ultimate Racing cats. They are very high quality and much beefier than RT cat construction. The fit is excellent. The sound is very nice with the NISMO exhaust. I have 200 mile on the cats and they are slightly louder and deeper than the NISMO exhaust. At wide open throttle they sound the same, but more exotic. There is absolutely no rasp.

I just wanted to mention my previous reveiw stated there was rasp near redline. This was vibration from a loose deflector under the car.

 

Most of them are the same, just go with a cheaper one, except Random Technology (those are known to break and fail).