Autolite AR12-4PK High Performance Racing Non-Resistor Spark Plug, Pack of 4 Replacement racing spark plug used by many professional car drivers Specifically designed colder than the factory plug to handle added power Contains an Yttrium-enhanced alloy to enable up to 8% reduction in sidewire temperature for improved durability and less pre-ignition Features cut back ground electrode for improved ignitability of flame kernel Coated in an anti-corrosive nickel plating to prevent rusting