Made from Chrome vanadium steel, tempered twice, High hardness, rustproof, solid and durable. Ideal to remove damaged, rusted or stripped screws, studs, bolts, fastener, metal water tap and water tube, etc. Sizes & Diameters: Drill bits' diameters and recommended extract diameters of broken screws are etched on the box for each tool. Remove Damaged Screws Bolts And Water Pipes - These extractors will remove most kinds of damaged, stripped, rusted, broken, or stuck screws from any wood or metal surface with relative ease. It can remove some of the common screwdriver can not be disassembled damaged bolts, screws, bolts and pipes.Reverse thread bits easily remove screws, bolts, studs, and threaded pipe fittings.