This 5pcs countersinks are suitable for drilling less than 25HRC hardness workpieces, such as carbon steel, sheet iron,insulation board, PVC board, hard woods, wood, etc. They can drill out sunk holes for screw cap while drilling the screw hole andkeep them on the same axial, also suitable for the drilling machines with collets or adapters. Features: 6 piece set includes 5 bits for drilling pilot holes for screw sizes #5 #6,#8,#10 and #12 and 1 hex wrench. Special designed HSS steel counter sleeve countersinks & counter bores pilot hole. Adjustable counter sleeve depth with allen wrench and 1/4" hex shank is quick change compatible. Pre-drilling and countersink to drive screws flush with the material surface or deep hole counter boring for driving screw headsbelow the surface. Drill and countersink for wood screws without changing bits, very convenient. Adjustable drilling length for various length screws simply by loosening and tightening the screw. Specifications: Color: Silver + Black Material: Carbon Steel + High Speed Steel (HHS4241) Hardness: HRC 60 Countersink Sizes: #5, #6, #8, #10, #12 Shank: 1/4"(6.35mm) Hex Shank Quantity: 5 pcs Drill Bits + 1 pc Small Wrench Chamfer Diameter: 10mm / 0.39" Countersink Diameter: 5# 1.98mm / 0.078" 6# 2.38mm / 0.09" 8# 2.78mm / 0.11" 10# 3.175mm / 0.125" 12# 3.56mm / 0.14" Countersink Length: 5# 54mm / 2.13" 6# 56mm / 2.20" 8# 61mm / 2.40" 10# 64mm / 2.52" 12# 69mm / 2.72" Item Weight: Approx. 71g / 2.50oz (6pcs set) Package Size: Approx. 7 * 5 * 1.1cm / 2.78 * 1.97 * 0.43in Package Weight: Approx. 73g / 2.57oz Package List: 5 * Countersink Drill Bits 1 * Hex Wrench