This diamond coated core drill bit removes a complete circle from glass， tiles， marble， granite， ceramic or otherMaterials and only needs water for lubricationCan be used with a standard electric drillAlways use lubrication (water)， otherwise the diamond core drill will burnStart your hole diagonally， make a round trace and then hold drill straightSize: 6mm， 8mm， 10mm， 12mm， 14mm， 16mm， 18mm， 20mm， 22mm，25mm， 26mm， 28mm， 30mm，40mm， 50mm.Quantity: 15 pcPackage includes:15 x Diamond Coated Hole Saw Drill Bits