DURABLE: This 4 piece spark plug thread repair kit is made from hardened carbon steel. RESTORES SPARK PLUG THREADS: It restores spark plug threads by re-tapping them and removing any carbon deposits. OVERHAUL CYLINDER HEADS: The set is also ideal for overhauling cylinder heads, especially those made from aluminium. SPARK PLUG THREAD SIZES: M10 x 1mm , M12 x 1.25mm , M14 x 1.5mm & M18 x 1.5mm. APPLICATIONS: Applications include garden machinery, mopeds, scooters, motorcycles, cars, vans and LGVs.