10Pcs 6mm (1/4") Diamond Coated Porcelain Ceramic Glass Hole Saw Drill Bit Extractor Remover Set Tools For Tiles Marble Glass Ceramic For porcelain, glass, marble, ceramic, rock and granite Excellent results in glass, marble, slate, and tile. Nickel plated. Segmented design works better and lasts longer Note: To prolong the life of these bits, use on a low speed with coolant (water/oil) No Pilot Drill Bit - Pilots are not safe for glass Cuts Through Ceramic, Porcelain, Glass, Marble, Granite,Wet Type - Do not use dry / Water is recommended for coolant