1. Multi-insulator-ribs prevent flashover. 2. The insulator consists of an aluminum oxide ceramic and insulates the central electrode up to 400000 V to ground. 3. Metal housing is made of steel and nickel-plated to provide protection from corrosion. Used to secure the spark plug in the cylinder head. 4. Conductive glass seal is electrically and thermally conducting and connects the terminal stud to the center electrode.