The only thread repair product that can be used to repair both taper seat and gasket type spark plug assemblies Three insert lengths are available to accommodate all spark plug reaches Positive mechanical locking feature means the insert will never come out! The piloted reamer tap means no drilling is necessary and perfect alignment of the tapped hole Available in kit or set for the do-it-yourselfer and professional engine rebuilderSav-A-Thread is the easiest way to permanently repair stripped spark plug hole threads Virtually all engines built today have aluminum cylinder heads Combining this with the growing number of do-it-yourselfers and the need for quick, easy, on-the-spot repairs makes Sav-A-Thread a must for every store and shop.