These 5pcs countersinks are suitable for drilling workpieces with hardness below 25 HRC, such as carbon steel, sheet metal, insulation board, PVC board, hardwood, wood, etc. They can drill hollow holes for plugs, keep them on the same axis, also suitable for drilling machines with collets or adapters. Features: 6pcs countersink set includes 5pcs bits for drilling pilot holes for #5, #6, #8, #10 and #12 screws and 1pcs hex wrench. Specially designed HSS steel countersinks and pilot hole. Adjustable sleeve depth with Allen wrench and 1/4" hex shank is quick change compatible. Pre-drilling and countersinking to drive screws flush with the material surface or deep counterboring to sink screw heads below the surface. Drill and Countersink for wood screws without changing bits, very convenient. Adjustable drilling length for screws of different lengths, 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 Drill Bits + 1 Small Wrench Chamfer Diameter: 10mm 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