Upgraded Dry Drilling Design : Diamond Drill Bit integrated with wax lubricant inside which melts while dry drilling and cools the cutting surface; Water can be used as additional cooling to prolong the life of the bit. Surface plating can prevent the drill bit from rusting Wildly Application: dry diamond drill set can be applied for drilling clean holes to hard materials, which especially fits well for tiles, porcelain ground, granite ceramic glass mirror marble stone masonry brick and so on; Note: not applicable to wood. Widely Compatibility: black diamond drill is designed in Hexagon Shank, which is compatible with most machines, such as hand drill, angle grinder, bench drill, also can be matched with side flutes help to remove debris and drill holes smooth and fast; Depth mark is also useful for precise project. Shank: Hexagon Shank colour: black Material: Diamond Coated, Alloy Package Contents: 2 x 3/16 inch (5mm) diamond drill bits diameter 1 x 1/4 inch (6mm) diamond drill bits diameter 1 x 5/16 inch (8mm) diamond drill bits diameter 1 x 3/8 inch (10mm) diamond drill bits diameter 1 x 1/2 inch (12mm) diamond drill bits diameter Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.