Replace the restrictive crushed factory down pipe on your 2017-2019 L5P Duramax with this 3.5" Down Pipe for improved exhaust flow. Connects to the DOC outlet flange behind the OEM turbo and mates with OEM exhaust system front pipe with the 4 bolt style flange connection. Black Ceramic Coated and Heat wrapped. Down Pipe includes bungs for sensors and NO tuning required to use this down pipe. WCFab piping kits and emissions compliant tuning recommended for optimum performance gains.