The Irwin Blue Groove 6X Drill Bits are ideal for drilling wood and offer 6 times faster drilling penetration than a standard flat bit. Their Tri-Flute design allows for faster chip ejection and their full screw tips ensure ease of use and pull through. The cutting spurs produce clean holes with minimal break out and the tapered flute reduces binding. The drill bits are also heat treated for extra durability. These extra long bits are 40cm (16in) in length, making them ideal for drilling through walls, ceilings and floors. Specifications:Diameter: 20mm.Working length: 10mm (4in).Overall length: 400mm (16in).