The U.S. E46 M3 exhaust system consists of 4 components: the headers (with integrated catalytic converters), section 1 resonator, section 2 resonator, and muffler. This item is designed to replace the section 1 cats, one of the biggest sources of the raspiness, these Supersprint Connecting "S-Pipes" help eliminate the raspy, tinny note classically associated with the sound of the E46 M3, especially when combined with Supersprint's X-pipe for the E46 M3. These will bolt to your factory headers.