SPECIAL SPARK PLUGS WITH SILVER MIDDLE ELECTRODE Spark plugs with a silver middle electrode, with a special construction, adapted to high thermal loads, vibrations and pressures. The open spark gap does not prevent the spread of the flame front and ensures perfect combustion of the mixture. Compared to conventional spark plugs of the same thermal value, the silver middle electrode allows (thanks to its high thermal conductivity) to use a larger area of the insulator tip and thus ensure a longer period of protection against clogging by conductive deposits.