O2 Oxygen Sensor Fitting Plugs or Weld Bungs 10 Steel Stepped Bungs M18 Standard Oxygen Sensor Weld Bungs, Mild Steel (M18 x 1.5 thread) Bulk O2 Oxygen Sensor Adapter M18X1.5 Weld on Bungs&Plug O2 Sensor Bung O2 Oxygen Sensor Weld In Bung & Plug M18 x 1.5 Stainless Steel Adapt. All Vibrant Performance exhaust bungs are made from the highest quality stainless and mild steel to ensure the utmost in quality for all professional aftermarket and O. E. M Exhaust projects.