NGK V-groove spark plugs offer perfect ignition of the air and fuel mixture especially in modern low emission lean-burn engines, even under extreme operating conditions. It has a 90° V-groove in the tip of the center electrode. It ensures that the spark is directed to the periphery of the electrodes. The flame core is generated near the perimeter of the electrode and grows. Ignitability is improved because the electrodes are interfering less with the growth of the flame core.