I have 2 Bros
Make no mistake, Im not a fan.
I may very well still have the fitment instructions showing it mounts to the footpeg..
Having said that, it comes with a 52mm midpipe which I thought was way cool for a ZX6.
Why I dislike it.... it sits right under your helmet and is noisy.. wear ear protection.
What I subsequently did was to rebuilt the whole thing. I used thin walled mild steel in 63mm diameter to create a new midpipe. 63mm is used in cars as well.. Then dismantled the silencer and replaced the perf with 63mm as well and made a new cap. The pipe is now longer and I moved the box back hanging from the footpeg.
The noise is behind me now..
Rebuilding the pipe with bigger diameter midpipe allowed bike better breathing at the higher rev range and showed real bhp increase.. it also showed me what a ripoff after market pipe cost really is.. our backyard word was a quarter of the cost
2-bros is like the GSXR of exhausts... I'll admit you can make power with it but it is just noisy and annoying as hell. I can't ride directly next to anyone that has one honestly since I avoid ear-plugs. I would recommend Brocks or Graves.
Gotta say, I've got a 2Bros collector back system with carbon can on my '06 10R and really like it. Keep in mind my other two bikes have full Akro and a titanium K-Factory header and 60mm midpipe with a hex carbon Akro can on it. My ZX10R sounds deep, not stupid loud below 6K but screams nicely at the top. YMMV.