The 2011+ Chevy / GMC Durmax LML is equipped with a Selective Catalytic Reduction (SCR). Removal of the SCR is one of the best things you can do to increase the life of your diesel pickup truck. Improve reliability and dependability by getting rid one of the weakest links on the GM Duramax. Removing the SCR will also make it so you no longer need to run Diesel Exhaust Fluid (DEF). The SCR and DPF are deleted together and must be done with a DPF delete capable tuner.