Features： 1、Firmly Inlaid at Top: The diamond on the top of the hole opener is firmly inlaid, not easy to fall off, low wear and tear, and can be used for a long time. 2、Thickened Alloy Carcass: The hole opener adopts thickened alloy carcass and has a universal round handle, which can be applied to a variety of models and has a wide range of applications. 3、Industrial Grade Carbon Steel: Hole opener made of industrial grade carbon steel, with nickel plated coating to resist corrosion, fine workmanship, super wear resistant, and pointed. 4、15 Sizes: This hole opener has 6, 8, 10, 12, 14, 16, 18, 20, 22, 25, 28, 30, 35, 40, 50mm sizes to meet various needs. 5、Uses: The hole opener is used to drill hard surfaces such as glass, wood, ceramic tile bottles, block jars, ceramics, slate, and granite pumice. Specification： Item Type: Diamond Drill Bit Set Material: Emery + Carbon Steel Model: Approx. 6mm / 0.23in, 8mm / 0.31in, 10mm / 0.39in, 12mm / 0.47in, 14mm / 0.55in, 16mm / 0.63in, 18mm / 0.71in, 20mm / 0.79in, 22mm / 0.87in, 25mm / 0.98in, 28mm / 1.10in, 30mm / 1.18in, 35mm / 1.38in, 40mm / 1.57in, 50mm  / 1.97in Package List： 15 x Hole Saw