The spark plug lead must reliably transmit the high voltage from the ignition coil so that the spark plug can reliably send a spark across its gap.
The TRD spark plug lead sets for the Corolla AE86 were developed based on the racing use concept. That is, achieve ideal resistance to enable a strong, steady spark, even under harsh conditions. We also used silicon rubber, with its excellent heat and water resistance characteristics. And, its color tone is red - to evoke the TRD image, which makes for an even hotter looking engine.
Ignition Lead kit - 7mm - Red