Downpipe Kit with 300CPSI Racing catalyst converter for Subaru WRX STI 2007-2018 made out of high quality stainless steel 1.4301 (SS304) complete � 76mm (3 " ) high quality 300CPSI Euro6 standard racing metal catalyst converter 100% perfect fit, plug and play less thermal load on the turbocharger more power by reducing back pressure significantly more torque