Under truck exhaust
Fit perfectly only had to make 2 cuts like it said in the instructions (make sure you read)

Key Features & Specs:
Fitment:
Upgrade your diesel truck with the MBRP S6005PLM ARMOR Lite downpipe-back exhaust system, built for 2001-2004 Chevrolet Silverado and GMC Sierra 2500/3500 models equipped with the 6.6L Duramax engine. This aluminized steel system features a 4-inch single side exit design with no muffler for a more aggressive exhaust tone and improved flow. Designed specifically for Extended Cab and Crew Cab configurations, it offers dependable performance and value backed by a 1-year warranty. This system is not intended for vehicles equipped with a catalytic converter.