Hey, Im in need of a cat for my exhaust system but im a little confused, i have rmf headers which are 2.5" outlet and a vision 2.25 cat back/b pipe. which cat do i get? A 2.5" or a 2.25"? Or do they make cats with one end 2.5" and the other 2.5"?? And also what brands and cell(100,200, highflow,etc) should i be looking for?

Thanks heaps