Drilax174; Small Diamond Coated Drill Bit Hole Saw Pick Size 1/4", 5/16", 3/8", 1/2", 5/8", 3/4", 7/8" in Inch Glass, Marble, Granite, Ceramic Porcelain Tiles, Bottles DIY Kitchen, Bathroom (Drill Bit Size - 1/2") Individual small diamond drill bits (diamond hole saws), you can select any size. Huge 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. Use a guide Tiles, Glass, Fish Tanks, Marble, Granite, Ceramic, Porcelain, Bottles Pick Any Size 1/4", 5/16", 3/8", 1/2", 5/8", 3/4" , 7/8" . Shank sizes vary, maximum shank is 3/8