Hello! new and could use some help.

thanks for reading my question. im new to the car customization world and im working on my 325i. i am currently looking at a exhaust swap and have my eyes on some ebay gear. the piping is 2.125". thus leading to my question. i kind of have my heart set on the remus twin 84mm tips muffler, but i cannot for the life of me figure out the inlet pipe size. and i have no idea if it would fit on the slightly larger pipes for the ebay gear. if anyone knows the answer it would be greatly appreciated, or if there are ways of "making it fit"