 Finally, in very recent years, a cup-style terminal has been introduced, which allows for a longer ceramic insulator in the same confined space.The main part of the insulator is typically made from sintered alumina (Al2O3), a very hard ceramic material with high dielectric strength, printed with the manufacturer's name and identifying marks, then glazed to improve resistance to surface spark tracking.Its major functions are to provide mechanical support and electrical insulation for the central electrode, while also providing an extended spark path for flashover protection.