Adapter, MBRP Exhaust Adapter, Universal Adapter, T409 Stainless Steel., 4in. OD, 3.5in ID. Adapter, T409, 4in OD, 3.5in ID. Adapter, T409 Stainless Steel., MBRP Exhaust Adapter, 4in Outlet Diameter to 3.5in. Inlet Diameter., Universal., Exhaust Pipe Adapter.