Size --- The diameter of the drill bit and the recommended diameter of the breaking screw are engraved on the housing. Please note that the screw thread direction is positive and the splitter thread direction is reversed. Turn the wire disconnector in counterclockwise will continuously tighten it in the inner hole and rotate the screw when some tightness is achieved. Easy to Use --- Aggressive left-hand (puller) and right-hand (drill) spiral groove design for extra grip. If the screws rotate in opposite directions, the screws will naturally break. (The 3mm screws can be difficult to work with) Versatile --- Broken screw extractor drills can also be used to drill holes in wood, metal, plastic, bricks and walls. High quality---Extractor set for screw removal use chrome vanadium steel which features high hardness, rust resistance and durability Convenient ---Ideal for removing damaged, rusted or stripped screws, studs, bolts, fasteners, fasteners, metal faucets and water pipes, etc. SPECIFICATION: Material: Chrome vanadium steel Diameter of the extractor: 1 for 1/8-1/4 (3-6mm) 2 for 1/4-5/16 (6-8mm) 3 for 5/16-7/16 (8-11mm) 4 for 7/16-9/16 (11-14mm) 5 for 9/16-3/4 (14-18mm) Drill diameter: 1: 5/64(2.0mm) 2: 7/64(3.0mm) 3: 5/32(4.0mm) 4: 1/4(6.5mm) 5: 19/64(7.5mm) Package includes: 5 x drill bits 5 x extractors 1 x holding key 1 x storage case