CTS Turbo F90 M5/M5C & F91/92/93/ M8 High-Flow Cats are made to maximize exhaust flow for highest power gains. Do not compromise performance and sound with factory parts. Designed using the latest in CAD technology; this part is made to fit perfectly in place of restrictive factory catalytic converter. Manufactured from CAST T304 stainless steel; hand TIG welded and back-purged to ensure years of reliable performance. In addition to unleashing the power and performance of your 4.4 Twin Turbo, our High-Flow Cats will make your vehicle sound like it really should. When installed with factory exhaust it produces a louder and deeper growl with much more pronounced exhaust “crackle” on downshift. While up-shifting you will enjoy a confident “punch!” as you bang through all 8 gears. The sound will be even louder if you already have an aftermarket exhaust system. Product Details: 80mm or 3.15″ diameter piping Cat size: 110mm OD x 90mm Long or 4.33″ OD x 3.54″ Long Includes 200 cell sport catalytic converter Designed and tested on a real car in the real world Cast T304 stainless steel, TIG welded back-purged construction Replaces restrictive factory catalytic converter Great power upgrade with uncompromising performance Incredible sporty exhaust sound, subtle when cruising No drone with factory exhaust.