APEXX 23601-01005 Porcelain Core Drill Bit with 5/8"-11 Female Thread for Porcelain/Granite / Marble Tile, 1" 1" Diameter, 1" Drill Depth Fits all popular various-speed angle-grinders with 5/8"-11 Thread Can be used on electric hand drills with 3/8" straight-shank adapter (sold separately) Maximum 3,500 rpm 2,800 - 3000 rpm is recommended Must use water. Use a sprayer bottle when drilling tiles on a wall