Denso Spark Plug Double platinum plugs offer long life and are typically called for on a DIS ignition system or where the plugs are particularly difficult to change. A fine platinum tip on both the center and ground electrodes allows for virtually no gap erosion, so that you will have optimum performance, longer. Double platinum was originally designed for the abuse of a Distributorless Ignition Systems(DIS), however any car can benefit from there long life high performance features. Copper core for better thermal conductivity. Machine rolled threads to reduce cross-threading and seizing . The plug insulator is constructed of purified alumina powder for extreme stress with 5 ribs to prevent flashover. Technical Specifications - 14mm Thread, 18mm (.708") Reach, 5/8" (16mm) Hex Size, Tapered Seat, Resistor, Solid Terminal, Platinum-tipped Ground Electrode and Platinum-tipped Center Electrode, Projected Center Electrode, .060" (1.5mm) Gap