Compatible with over 150 models of lawn equipment, this Spark Plug has been sourced directly from the original manufacturer. It is sold individually, made of metal and ceramic components, and is not part of a kit or assembly. The spark plug is used to ignite the air-fuel mixture inside the combustion chamber. You may need to replace the Spark Plug if your 1 cylinder engine won't start, or if your more-than-1 cylinder engine runs rough. Spark Plugs will wear over time and should be inspected regularly. Customers rate this repair as Easy.