CPR features a range of different styles of high-quality O2 Sensor weld-on bungs and plugs to fits M18 x 1.5 mm The oxygen sensor bung is a must-have accessory for installing your wide-band oxygen sensor. Are making custom Exhaust and headers CPR welded in O2 Sensor bungs in your system for data logging, engine management, and dyno testing? Fits Bosch 0258007057 / LSU4.2, Bosch 0258017025 / LSU4.9 This range of bungs and plugs is available in materials 304 Stainless Steel.