UPR O2 Oxygen Sensor Weld Bung is a great way to add a sensor for stand alone wideband, adapting a new exhaust to your EFI system or for tuning your carbureted engine. This bung is CNC Machined from Stainless Steel with an 18mm-1.5mm thread size which fits most vehicle manufacturers oxygen sensors as well as some common aftermarket sensors found in Holley, Fueltech, Haltech, Bigstuff EFI systems and Innovate wideband kits (see list below).