Stainless Bros SS304 O2 oxygen sensor weld bungs are perfect for adding a Wide Band O2 Oxygen sensor to your factory or custom fabricated Stainless Steel exhaust system. The Stainless Bros O2 sensor bungs are CNC machined out of the high quality 304 Stainless Steel and come pre-coped specifically to fit 2.75" to 5" tubing for ease of use.