Diameter: 3/8 inch, shank: 1/4-inch (10mm diamond drill bit) Shank: 1/4" hex shank. These 3/8 diamond drill bits are part of the Quick Change universal hole saw system, which lets you change hole saws in seconds. MUST USE WITH WATER throughout the process. Recommended used at a low speed and low pressure.For cool cutting lubricate with water for extended life. Wide application: 3/8 inch diamond hole saw drill holes in glass bottles, tile, porcelain,ceramic plant pots,granite,marble slab and stones. DaduoRi 3/8 inch 10mm Diamond Drill Bits with Hex Shank for Glass Granite Porcelain Tile Ceramic Marble Stone, 2 Pack