HQMaster Titanium Step Drill Bit, High Speed Steel HSS Quick Change 1/4" Shank Total 28 Sizes 3-Piece Set Tool for Carbon Steel, Sheet Iron, Insulation Boards, PVC Boards, Planks, and Wood TITANIUM | HIGH SPEED STEEL: Suitable for below 25 hardness of the work piece, such as carbon steel, sheet iron, insulation boards, PVC boards, planks, and wood thickness below 5MM Quick-change 1/4" hex shank TWO-FLUTE DESIGN: made the penetration faster without chipping This compact set replaces 28 individual drill bits SET INCLUDES: Bit #1 (6 steps): 3/16", 1/4", 5/16", 3/8", 7/16", 1/2"; Bit #2 (13 steps): 1/8", 5/32", 3/16", 7/32", 1/4",9/32", 5/16", 11/32", 3/8", 13/32",7/16",15/32",1/2"; Bit #3 (9 steps): 1/4", 5/16", 3/8", 7/16", 1/2", 9/16", 5/8", 11/16", 3/4"