The Irwin Blue Groove 6x drill bits are ideal for drilling wood and offer 6x 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 stubby drill bits are 10cm (4in) long, making them ideal for drilling through joists or in enclosed areas. Suitable for holes up to 5cm (2in) deep.5 Piece Stubby 6X Blue Groove Wood Bit Set 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 tampered flute reduces binding. The drill bits are also heat treated for extra durability. Comes with an extension. These stubby drill bits are 10cm (4in) long, making them ideal for drilling through joists or in enclosed areas. Suitable for holes up to 5cm (2in) deep.Sizes: 16mm, 18mm, 20mm, 22mm, 25mm.