Spark Plug wire 9 for Mercury and Mariner Premium Marine Wire Leads Magnetic Suppression Core Manufactured for your specific application 9 length Metallic core wire. 7mm copper core wire Durable stainless steel wound conductor for maximum horsepower and engine performance. Premium silicone jacketing and boots for the ultimate in high temperature protection. Superior RFI suppression for the most sensitive electronic system. Corrosion resistant stainless steel spark plug and distributor terminals