Lang M12 Spark Plug Thread Restorers is used to clean up dirty or damaged spark plug threads on Harley- Davidson® TwinCam®, V-Rod® and other Sportster® models service all major vehicle platforms using 10mm and 14mm spark plugs. Lang rethreaders restore and clean threads of dirt, carbon build up, and metal particles. Lang spark plug thread restorers comes with a rubber o-ring to firmly hold it into the socket.