ARP's Spark Plug Indexer takes the guess-work out of installing spark plugs where the combustion chamber and high dome piston clearances is critical. Fitting in the palm of your hand, this tool is designed to eliminate the need to perform cylinder head calibration. Made from aluminum alloy, the indexer has precision machined threads that allows you to proof the quality of spark plug threads before installation in cylinder heads. Comes anodized for protection and quick recognition. For use with tapered gasket 14mm plugs.