Drilax&trade; 5 Pcs Diamond Drill Bit Set 3/16", 1/4", 5/16", 3/8", 1/2" - Wet Use for Tiles, Glass, Fish Tanks, Marble, Granite, Ceramic, Porcelain, Bottles, Quartz - Lot 5 Diamond Coated Drills - Kitchen, Bathroom, Shower, Lamps Drilax050513 5 Mostly Used Sizes: 3/16", 1/4", 5/16", 3/8", 1/2" -High Quality Diamond Drilling Tool Set of Over 80% cost savings compared to big box stores. Use with standard electric or battery drillers. There is no need for a center pilot drill. These tools do not have center pilot drills. Do NOT run dry. These Diamond Coated Tools will work best if you use water to keep the tools cool. Shank sizes vary, maximum shank is 1/4" - suitable for all common electric drillers.