The NGK range of resistor covers are designed to give perfect noise suppression across all frequencies whilst engine performance is not adversely affected. The construction is extremely durable and the resistor element is long enough to prevent interior flash-over and steady resistance is maintained. Superlative ceramic materials are incorporated that resist deterioration and have small resistance variation under over-load, whilst the plug connector is made of sturdy phenolic resin or EPDM rubber which are oblivious to tremendous heat and high tension. The heat press insertion technique makes the construction all the more tough and vibration resistant. Special rubber liners on both ends prevent moisture from causing electrical leakage.