Material Made from high performance chrome molybdenum and solid cast steel construction for strength and durability Finished with Black Oxide to prevent rust. Application Widely used for cleaning and rethreading damaged spark plug hole. Cleans damaged spark plug ports and threads. Rethreads damaged spark plugs, eliminates corrosion and straights damaged threads. Reduces the chance of cross threading. Size 1* M18 x 1.5mm and 1* M12 x 1.25mm thread chasers with 38 drive to clean and repair damaged threads. USE Use with 34 hex socket or 38 square drive. Size M18x1.5 Also works on M18x1.5 spark plug threads; M12 x 1.25 Also works on M12x1.25 spark plug threads. Service 100 satisfaction guarantee, If you have any issues with the part, simply contact customer service for troubleshooting help, parts, replacement, or refund. Our aim is to make you satisfy the parts and the service we provide for you.