6 Pcs 1/4" Hex Shank 5 Flute Countersink Drill Bit – Made of high-speed steel, they are perfect for sinking 90° holes in Wood and PVC board. Diameter- 6mm, 8mm, 9mm, 12mm, 16mm, 19mm. Suitable for drilling holes in iron plates, copper plates, aluminum plates, wood, PVC sheets, and insulation boards.