The spark plug bungs offer two different ways to mount the spark plug to the tailpipes. The best way is to weld the bungs to the tailpipes so that the spark plugs can be removed for cleaning, or be replaced. This offers a solid ground connection for the spark plugs. However, the spark plug bungs can be used as nuts to secure the spark plugs from the inside without the need of welding. However, this technique may cause grounding issues if not properly tightened down.