Black Onyx coating helps reduce corrosion Copper core provides great heat transfer and helps maximize plug durability Ribbed suppressor seal extends resistance and helps prevent spark 'flash over' and misfires Nickel-chrome alloy sheathing helps prevent corrosion on center electrode Available for use in Marine applications Some ACDelco GM Original Equipment parts may have formerly appeared as GM Genuine Parts (OE) or ACDelco Professional ACDelco GM Original Equipment parts are designed, engineered and tested to rigorous standards, and are backed by General Motors GM Engineers design and validate OE parts specifically for your Chevrolet, Buick, GMC, or Cadillac vehicle GM regularly updates production and service part designs to integrate new materials and technologies