This is the single most important aftermarket performance part for an M3 and you must refuse to go cheap. The x-pipe is the only mod in an M3 that provides a significant power gain. That x-pipe (which they call h-pipe), looks to be made out of tin can and looks to be 1" OD. Literally.
Spend a little more and a buy a proven X-pipe. I know $2,000 for an xpipe is quiet significant but try a second hand one if you can't buy new. This pipe can damage the O2 sensors, break at the flanges, weldings, cause leaks... It could be a nightmare.