The AFE 48-34139 Twisted Steel Headers With Up-Pipes & Down-Pipe will help you get the maximum flow out of the heads & turbo in your 2011-2015 GM 6.6L Duramax LML. This up-pipe & down-pipe kit features headers that are constructed out of 2” mandrel-bent 304 stainless steel tubing with a .120" wall and the down-pipe is built with 3” mandrel-bent 304 stainless steel tubing for durability and longevity. The up-pipes use heavy duty 4" 304 stainless steel flex tubes with internal interlock liners for improved flow and improved durability. The AFE 48-34139 Twisted Steel Headers With Up-Pipes & Down-Pipe utilize optimized tube lengths with mitered collectors for true pulse control technology that enhances flow and horsepower across the RPM range. With two exhaust gas temperature (EGT) ports to choose from - 1/8” NPT EGT in the the driver’s side manifold and a M14x1.5 port in the down pipe – monitoring the vitals of the engine is a simple task. EGR mounting flanges are retained, a CNC-machined v-band inlet flange and the use of all the factory mounting locations makes this kit a true bolt-on system with no cutting or drilling required for installation. FEATURES: Made In The USA Direct-fit Replacement 1/8" NPT & M14 EGT Ports Retains EGR Mounting Flange 304 Stainless-Steel Construction 2 Year Limited Warranty Application Note: This item will not fit models manufactured after July 2014 equipped with a 3-bolt flanged down-pipe. Not available for sale in the state of California Not available for sale in the state of California. Click here to read Emissions Notice.