The Irwin Blue Groove 4X flat bits have a patented groove point and cutting edge. The cutting edges cut the timber 4 times faster, without scraping. The parabolic scoop optimises control and removal of wood chips. These flat bits have an increased relief angle from 12° to 17°. The shank is 152mm long and 10% larger in diameter for added durability. The Irwin IRW10506629 8 piece Blue Groove 4X flat bit set includes the following sizes: 12, 16, 18, 20, 22, 25, 28 and 32mm diameter.