8mm Ferro-Spiral core wire now has ceramic boots on the spark plug end that can withstand up to 2,000 degrees F. If you are running headers with close tolerances, have an engine bay with little room or an RV with boots that melt because of heat, these wire kits are the answer for burnt and melting boots.The Extreme 9000 Ceramic Wires also feature stainless steel spark plug terminals for maximum spark energy to the plugs.