The same spark plugs that were installed when the engine left the assembly line. Spark plugs are matched to the engine for optimum engine performance. Spark plug design features fine-wire double platinum pad on both electrodes. High melting point provides excellent resistance to erosion. (Roushcharged Raptor 575 & 2.3L EcoBoost)  This part number is for a set of 16 spark plugs.  For a single spark plug use 597128.