This IRWIN HANSON 536/526 Series 5-Piece Straight-Flute Screw Extractor Set is designed for softer materials or thin-walled pieces, such as pipes and fittings. The design on these screw extractors eases extraction because it does not expand the material as it is removed. Each IRWIN screw extractor can remove both left-hand and right-hand threaded parts and has the size and recommended drill bit size etched onto it. 5-Piece Hanson Straight Screw Extractor Set, contains sizes ST-1-through ST-5, for removing broken screws, studs, and bolts. The straight tapered flute will not expand the piece being removed, but removes the broken piece without damage to threads. The correct drill size is stamped on each screw extractor. Irwin tools are made of only the finest materials, manufactured to exacting tolerances.