Keep the check engine light off with MagnaFlow HM Grade Federal/EPA Compliant Direct-Fit Catalytic Converter 50400. DIY installation is easy with the proper tools (no cutting or welding required). With features including mandrel-bent tubing to eliminate flow restrictions and stainless steel construction to resist corrosion, you can have confidence in the quality of this catalytic converter. Using state-of-the-art 3D scanning systems in the design process, the MagnaFlow metrology department ensures this new part to fit and function like the original equipment. Designed to fit the 2004-2005 BMW 645Ci, 2004-2005 BMW 545i, and more, this direct-fit catalytic converter also interchanges with OE parts 18 40 7 522 555 and 18 40 7 522 571. Hardware is included to eliminate the hassle of working with corroded factory parts. This replacement part is designed to meet or exceed Federal emissions requirements set forth by the EPA, complying with legal standards for OBDII Federally registered vehicles with Federal/EPA Emission systems.