The Irwin Diamond tipped drill bits are suitable for fast smooth cutting in all grades of hard and soft tiles. Their raised diamond grit edge makes for easy starting in hard tile without the need for a guide. The diamond grit is tough brazed diamond which ensures fast cutting and long life. The drill bit’s reverse spiral forces water towards its cutting head, keeping the diamonds cool to increase cutting speed and prolong life. Drilling with water will further increase the lifespan of the tool. The auto slug ejection slot allows the bits to be used for continuous, uninterrupted cutting.The Irwin IRW10507900 Diamond Drill Bit 4 Piece set comprises one of each of the following diameters:5, 6, 7 and 8mm.