The B&B is all stainless steel. They have 2 versions. Justin, my neighbor with the M3, said that one version was the quiter one. He bought the new system which is louder. It sounds really nice. There is this other neighbor with a Viper......anyways Justin pulled up right behind him . We got out and asked the Viper owner to turn on his car....we wanted to see which one idled louder. I am not kidding but his M3,B&B modded, was louder at idle.