Size---The drill diameter and recommended breaking screw diameter are engraved on the case. Please note that the direction of the screw thread is positive and the direction of the separator thread is reversed. Rotating the wire separator counterclockwise will continuously tighten it in the inner hole and rotate the screw when a certain tightness is achieved. Easy to Use---Aggressive design with spiral groove for left hand (puller) and right hand (drill) for extra grip. If the screws rotate in opposite directions, the screws will naturally break. (It may be difficult to work with 3mm screws.) Versatile - Broken screw extractor bits can also be used to drill holes in wood, metal, plastic, bricks and walls. High Quality --- Screw removal extractor set made of chrome vanadium steel, which offers high hardness, rust resistance and durability Practical --- Ideal for removing damaged, rusted or worn screws, bolts, studs, fasteners, brackets, metal taps and water pipes, etc.