Professional tool for commercial or occasional use. Ideal for restoring damaged threads. This M5 – M12 thread repair set is suitable for engine repair and other automotive applications. Manufactured from chrome vanadium steel for strength and durability. Suitable for steel, cast iron and aluminium. This kit is simple to use. It involves drilling to clear the damaged threads with a standard drill (included). For repairing a spark plug thread, no predrilling is necessary if using the special spark plug tap; please pay attention that for flute-less taps, bigger holes are required. Check that the thread and pitch of the tap and the bolt match. For tapping, use the special taps for cutting the holding thread into the cleared hole (it is recommended to use a suitable cutting oil). To install the insert, place the insert on the installation tool and position the adjustable ring so that the insert tang is centered in the tang slot. Wind the insert in with a light downward pressure until it is a half turn below the surface. Do not work against the thread direction, as the tang could break. For tang removal, after finishing, lift the installation tool and use the tang break tool to remove the tang. For bigger sizes and spark plug taps, use long-nose pliers to remove the tang. Due to the narrow and exact tolerances, the new thread is normally stronger than the original ones. The set includes the following sizes: M5 x 0.8 x 6.7mm (x 22 inserts), M6 x 1.0 x 8.0mm (x 22 inserts), M8 x 1.25 x 10.8mm (x 22 inserts), M10 x 1.5 x 13.5mm (x 22 inserts), and M12 x 1.75 x 16.3mm (x 22 inserts). The set also includes: 5 x installation tools (various sizes), 5 x break pin tools (various sizes), 5 x HSS twist drills (various sizes), 1 x Allen key, and 5 x taps (various sizes). Comes in a metal tin for easy storage and transportation.