Replacing stripped or damaged 02 sensor ports? Adding an 02 sensor bung to a newly fabricated exhaust? This notched 02 sensor bung is what you need! The notched cut gives you ease of welding by letting it sit on a rounded surface much easier. Made from 304 stainless steel, using the popular size of 18mm x 1.5mm thread. This bung will accept most standard 02 sensors from most manufacturers.