Champion RF10C Copper Plus Marine Spark PlugChampion marine spark plugs are quality OEM replacements. The Champion RF10C Spark Plug features a copper core electrode that provides increased conductivity and heat control for good overall wear. These marine spark plugs are designed to resist overheating under heavy engine loads. Copper Plus for dependable performance; Copper core electrode allows for accurate control of heat range for longer life; Patented TinTac and ULTRASEAL coated shell for maximum corrosion resistance; Patented SAC-9 semiconductor for maximum EMI & RFI suppression.; Built to ISO and SAE standards for proven performance.Application: Mercruiser; 215 8 cyl; 225 8 cyl; 233 8 cyl; 255 8 cyl; 888 8 cyl; OMC; All Models, 18mm tapered seat;