I ordered this 50054 after speaking to Flowtech tech support. They confirmed that the muffler is a 3 inch core with 3 inch inlets and outlets. After receiving them, I measured the inner core. There's a 2.25" limit right at the inlet, and the baffles are just over 2.25" - definitely not a 3" core and not as advertised. If you're building a 3" system, look elsewhere for mufflers.