Dieselr Aluminized 4" Cat Back Exhaust Single | GM 2500/3500 6.6L DURAMAX LML 2011-2015The Dieselr Aluminized 4" Cat Back Exhaust Single (20112015 6. 6L Duramax LML) is engineered for GMC Sierra and Chevy Silverado 2500 3500 HD owners who expect dependable fitment, efficient flow, and long term reliability. Built from 4 inch heavy gauge aluminized steel, it increases exhaust velocity, reduces EGTs, and delivers a refined diesel tone that means business. Each Dieselr system is mandrel bent for unrestricted flow and precision welded for