MR43T spark plugs come pre-gapped as specified by your engine manufacturer. Use only the spark plug listed in your engine owner’s manual. Using the wrong plug can reducing optimum performance, reduce fuel economy or cause damage to your engine. Spark plugs are easy to change with common spark plug sockets. The AC Delco Ribbed Suppressor Seal extends resistance and prevents spark “flash over” and misfire. They feature a copper-core center electrode that helps provide improved heat transfer to the tip, giving you the reliability youre looking for while improving its resistance to low-speed carbon fouling. The AC Delco exclusive Hot-tip insulator heats fast and fires hot to promote longer electrode life for miles of dependable performance.