Semi shallow discharge candles

Semi shallow discharge candles:

These are candles that do not have a side electrode, the spark occurs between the central electrode and the metallic castle. They are applied to specific engines such as Formula 1. Where mechanical vibration requirements are very high.

This is due to the high level of engine vibration, which can cause the spark plug side electrode to break by resonance., excessive vibration causes electrode breakage due to mechanical fatigue.