5/8 x 11 Threaded Adaption Vacuum Brazed Segment Stainless Steel Drill Guide Hex Shaft Adapter designed for both porcelain or stone.  Set comes with 1/4" 6mm, 1/2" 12mm, 3/4" 20mm, 1" 25mm, 1 1/4" 32 mm, bit guide and hex shaft adapter can be used with a drill or a grinder. core bit