For professional workshop use. Hand tool used to restore up to 60% damaged threads on bolts; studs and other external threaded parts. Comes with special hardened HSS tool steel blades. Installs to the thread diameter by rotating the serrated knob; after which the bolt is rotated in the tool. Automatically adjusts to the thread pitch since the blades are guided by chasing undamaged sections of the threads. Compatible with M4 to M19 or 5/32" to 3/4" diameter threads. - Professional choice for workshop use - Dual cutting blades; hardened HSS tool steel - Auto guided by existing threads - Removes rust and burrs - Automatically chases good threads to repair / re-groove damaged sections - Hand tool - For any thread diameter; inch or metric from M4 to M19 or 5/32" to 3/4" - For any pitch - For right or left-hand threads