Champion Spark Plug 25-4PK Copper Plus Replacement Spark Plug, 4 Pack Dependable and durable Built to ISO and SAE standards for proven performance Patented SAC-9 semi-conductor resistor for maximum EMI &amp; RFI suppression Copper core center electrode allows for accurate control of heat range for longer life TinTac and ULTRASEAL shell for best corrosion protection of any spark plug in the industry.