MBRP 2001-2005 Chev/GMC Duramax 6.6L Regular Cab 4in Extension-Pipe AluminizedMBRP 2001 2005 Chev GMC Duramax 6. 6L Regular Cab 4in Extension Pipe Aluminized Some folks are just not satisfied with the usual. They have to always be pushing the limits; refining and adjustments; until they have the truck that has no limits. We have put together some components that will take your truck to the next lever. Armor Lite Exhaust Adapter; 4 in. Diameter; Aluminized; 4 in. Outlet Diameter Tip; Regular Cab Adapter. Fitment: Chevrolet