CTA Tools 98141 Pro-Thread 14-Millimeter Spark Plug Repair Kit - Tapered Seat is designed to repair 14-millimeter, tapered seat and gasketed spark plug ports in aluminum and cast iron heads. No drilling is required. The kit includes a tap, an expanding tool and one each of 3 sizes of inserts (1/4-inch, 3/8-inch and 5/8-inch). 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.