Delta Diamond 1/4-inch Diamond Hole Saw Drill Bits for Porcelain Tile Ceramic Tile Glass Stone Granite Marble Stainless Steel (1/4") Use this bit to make holes in a wide range of applications from hard porcelain tile, ceramic tile, glass, marble, granite, stone, slate, limestone, terrazzo, quartz, stainless steel sinks, glass jars and anything similar. Made with GE Super-Abrasive vacuum brazed diamond coating with a high-speed steel core these professional grade bits last 20-30 times longer than conventional lower-quality plated bits. Expect a long tool life and excellent performance, making for a clean and accurate hole for a professional-grade job. Vented side opening allows user to spray water on the drilling surface. Bits may be used wet or dry. However, spraying water on the drilling surface helps keep the bit cool and reduces friction, producing a better result. Size: 1/4" X 3/8" Shank. ~1" drill depth. Use with low RPM variable speed drills for best results. (300-500 rpm) Because this is a top-quality product it is backed with a 100% lifetime warranty that also includes free return shipping. If it ever breaks, warps, cracks or shows any sign of a material defect (being used for its intended purpose), or if the bond between the diamond segment and the steel core becomes separated at any time, it will be replaced free of charge! (Look for items "Sold By Delta Diamond Products, Inc")