CTA Tools 2361 Spark Plug Hole Thread Chaser - 14-Millimeter/18-Millimeter is designed to remove carbon and corrosion from both 14-millimeter and 18-millimeter spark plug holes. It also straightens damaged threads. Use with 13/16-inch deep socket, open end or box wrench. This tools features tapered ends for easy starting. Heavy-duty construction allows for strength and durability. Whether tuning up your '68 Corvette or changing the oil on a John Deere tractor, CTA can supply you with the tools needed to do the job. California Prop 65 - Warning, This product contains chemicals known to the State of California to cause cancer, birth defects or other reproductive harm.