2015-2016 Ford Mustang GT (5.0 V8 Models) 3" Complete Long Tube Header System (With Cats) Roush Complete Header packages are designed for customers looking for more power from their vehicle. Made from 304 stainless steel, these Roush Headers are built last and look great. Their 1 3/4" primary tubes and 3" collectors are designed for maximum power. Catalytic converters are integrated into the system and X-Pipe, 02 extensions, gaskets, hardware, and detailed installation instructions are all included. The part number for this item is Roush 421947 and it fits 2015-2016 Ford Mustang GT (5.0 V8 Models).