Smooth polished onyx gemstone. Flat back round cabochons, suitable for gluing into bezel settings, onto flat back bails, even directly on to fabric. There are many suitable adhesives - one that we recommend is E6000. Cabochons have a flat back and are not drilled. These are a classic round shape with a smooth surface and they are a standard size that fits many styles of setting, both vintage and modern. Please check dimensions to make sure they will fit your project. Approximate Measurements: 25mm in diameter. 6-7mm thick. Quantity: 1 Cabochon Due to the nature of this gemstone, there will be some variation amongst the pieces, including inclusions and color."