Specification:Material: 45Carbon SteelShank: 3/8 inch(10mm) Round shankSizes: 1/4 inch(6mm),3/8 inch(10mm),1/2 inch13mm),5/8 inch(16mm)Features:The set includes two shapes, four sizes of drill bits to meet your different work needs in daily useMade of high grade carbon steel, accuracy manufacturing, high strength, smooth surface and corrosion resistanceCan be used with hand and bench drills, but for best results, use a drill press for increased efficiencNote:Suitable for hand drills and bench drills, but for best results use a drill press for efficiency For your safety, please do not use too fast, bench drill speed should not be too fast, easy to produce smoke and burns Package Includes: 4 pcs Standard Plug Cutters4 pcs Four Tooth Chamfered Cutters