Operation Tips for Vacuum Brazed Diamond Drill core bits 1.Do not use these drill bits with hammer mode. 2.Only fit these drill bits on a cord drill, not cordless drill(no enough power). 3.Only for tile drilling not recommend for the material behind the tile. 4.For horizontal drilling,just give a gentle pressure,For vertical drilling, the weight of the machine will give sufficient pressure. Colour:Black Material:Diamond Size:6 / 8 / 10 / 12mm Package Contents: 4 x drill bits Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.