MBRP's 4" Cat-Back SLM Series Exhaust System for your 2001-2007 GMC Chevy 6.6L Duramax LB7, LLY, and LBZ diesel pickup is made from 16 gauge T409 Stainless Steel, which lasts longer than aluminized steel exhaust kits. This free-flow exhaust kit does not come with a muffler or exhaust tip.