General description High quality diamond powder lapidary drill bits, precise and durable. Ideal for drilling holes in materials such as jewelry, ceramics, jade, agate, glass, amber, and semiconductors. Technical specifications Size: 1-1.1mm Quantity: 20 pieces per pack Usage The higher the speed of the drilling machine, the better the effect of the drill bits. Drilling machine speed should reach 2000 rpm for optimal performance. Use cold water during the drilling operation to enhance effectiveness. If the drill bit becomes dull after multiple uses, you can cut the top slightly with pliers to restore sharpness.