Description: Made of high speed steel, sturdy and durable. Great for making countersunk holes, DIY daily use, easy to use and effectively to drill without burr. Suitable for processing metal and some non-metallic materials, such as PVC board, aluminum, plastic, iron. Used for workpiece circular aperture chamfering or cone hole, the edges on the surface of the chamfering processing. 4 types to meet your different needs: 9.7mm(0.38inch), 14mm(0.55inch), 21mm(0.83inch), 28mm(1.10inch) (countersink top diameter). Specification: Material: HSS High Speed Steel Inclined hole chamfer: 2-5, 5-10, 10-15,15-20 2-5: Suitable for holes in the range of 2mm-5mm( 0.07inch-0.20inch)，6mm(0.24inch) handle, 9.7mm (0.38inch) Diameter of top 5-10:Suitable for holes in the range of 5mm-10mm(0.20inch-0.39inch)，8MM(0.31inch) handle,14mm (0.55inch) Diameter of top 10-15: Suitable for holes in the range of 10mm-15mm(0.39inch-0.59inch), 10mm(0.39inch)handle, 21mm (0.83inch) Diameter of top 15-20: Suitable for holes in the range of 15mm--20mm(0.59inch-0.79inch)，12mm(0.47inch) handle, 28mm (1.10inch) Diameter of top Package Includes: 8 Pieces Chamfers Drill Bits