The Ace Race Parts brand of metric Oxygen (O2) Sensor Bungs is precision machined using solid 1018 Mild Steel bar stock and work with all standard O2 Sensors that use a M18 x 1.5 thread. This specific O2 sensor bung fitting features a Stepped design for added weld strength. Our O2 sensor bungs and bung plugs are a high quality mild steel option for custom exhausts, downpipes, and OEM repair fabrication projects.