NGK Motorcycle spark plug R7376-9 = R6252E

Racing Spark Plugs

Racing spark plugs need to withstand particularly high voltages. Engine speeds during a race often exceed 15,000 rpm. The temperature, pressure, and vibrations in the combustion chamber are so significant that conventional ground electrodes could break or melt.

That's why racing spark plugs are often fitted with ground electrodes specially designed for competition, with the most extreme form featuring a ring ground electrode. The spark "jumps" from the central electrode to the ring ground electrode.