Drilax&trade; 5 Pcs Diamond Drill Bit Set 1/2" (0.5 In) Wet Use for Tiles, Glass, Fish Tanks, Marble, Granite, Ceramic, Porcelain, Bottles, Quartz - Lot 5 Diamond Coated Drills - Kitchen, Bathroom, Shower, Lamps Drilax051313 Premium Diamond Drilling Tool Set of 5 1/2" 0.5 inches - Lot of 5 Diamond Drill Bits Best value for 1/2 inch diamond bits. Use with standard hand or upright drillers. These tools do not have center pilot drills. And there is no need for a center pilot drill. Do NOT run dry. Diamond Coated Tools will work best if you use water to keep the tools cool. Shank size is 3/8" - suitable for all common electric drillers.