Quickly and easily restore stripped or damaged spark plug port threads to original dimensions with our Helical Screw Thread Inserts. Spark Plug Inserts are the preferred method of repair by nearly all US & foreign auto manufacturers. Coil tension securely holds the insert in place without undue tension on the surrounding material. The inserts are vibration and impact resistant so won't strip or seize. Made from corrosion resistant stainless steel, they offer a wide temperature tolerance.