Outfit your semi truck to be Ready for the Road Ahead with a fast and responsive engine startup, with the Denso Iridium Saver On Highway Natural Gas Spark Plug and Boot Kit. By creating a high-voltage electrical spark inside of a combustion chamber, this replacement component is able to ignite the combustion process that powers an engine. Constructed with a precisely-manufactured center and electrode gap to reduce the need for frequent changes. FleetPride is your First Click in Heavy Duty .