Made of chrome-vanadium steel, high hardness, rust-resistant, strong and durable The recommended drill bit diameters and extraction diameters for broken screws are engraved on the housing. The extractors and drill bits have a strong gripping force. Ideal for removing damaged, rusted, or stripped screws, studs, bolts, fasteners, metal water taps and pipes, etc. The drill bits can also be used to drill holes in wood, metal, plastic, brick, and walls, etc.