Racing Beat s ULTRA 8mm wire sets are constructed with zinc-plated high-strength copper wire to prevent corrosion. Threaded brass connectors are crimped to all wire ends to provide a superior connection. The silicone rubber used will handle over 100,000 volts and is capable of withstanding temperature ranges from -60 F to +480 F over exceptionally long periods. ULTRA Ignition wire sets have a wire wound resistor encapsulated in each spark plug boot. This feature reduces electromagnetic radiation.