Ignition leads, also known as spark plug wires, deliver high-voltage electricity from the ignition coil to the spark plugs, initiating combustion within the engine cylinders. These multi-strand copper core cables are sheathed in silicone or PVC for dielectric strength and heat resistance. Internal resistance is tightly controlled to maximize spark energy; lower resistance values improve combustion efficiency. Leads are terminated with conductive terminals securely fitted to both the coil and spark plug ends, ensuring consistent current flow. Length and terminal angles vary based on engine configuration and spark plug location.