Osko&reg; 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, Lamp 45# Steel Base and Type 3 Diamond,For porcelain, glass, marble, ceramic, rock and granite 5 Mostly Used Sizes: 3/16", 1/4", 5/16", 3/8", 1/2" -High Quality Diamond Drilling Tool Set of Shank sizes vary, maximum shank is 1/4" - suitable for all common electric drillers. Do NOT run dry. These Diamond Coated Tools will work best if you use water to keep the tools cool These tools do not have center pilot drills. There is no need for a center pilot drill.