The Mayhew Tools Spark Plug Thread Chaser, No. 37900, is designed to clean and restore damaged spark plug holes, either 18mm by 1.50mm or 14mm by 1.25mm. By placing the spark plug thread chaser into the impacted area and using a 3/16" ratchet or deep socket, users can effectively engage with the threads to clean and restore them. Additionally, the Spark Plug Thread Chaser features a rubber O-ring, preventing unnecessary slippage and ensuring correct alignment while in use. A black nitride finish helps prevent rust and provides corrosion and abrasion resistance. Made in the U.S.A.