It is not one piece, it has a slip fit joint on the 'H' but it is very tight, no clamp needed. My pipe (O/R H ) was done very nicely and I had only a slight leak on the drivers side socket. The only thing I needed was some smaller SS bolts for the cat back. It comes with 3 inches and I needed 2 1/2 inches. Other than that it took 2 hours to install. Get some PB blaster.
My friend recently installed an MRT H-Pipe and said qaulity was great, no fitment issues or any problems at all. He did it himself and it took him like 3 and a half hours. He was going to get and X-pipe but he says my car sound is to "raspy" for his taste.
I have it - very nice. The first time I installed it I had some leaks. Turns out I didn't have the H-pipe together enough and it made it nearly impossible for the H-pipe to seat properly on the manifolds. Correcting my assembly error made all the difference in the world. I had to use a little high-temp rtv sealant on the driver's side manifold/h-pipe connection, but I think that was due to the JBA headers.