Shop name:Chong Qing Shuo Yue Ke Ji You Xian Gong Si Brand new and high quality. Easy to use, high quality,good performance, . Can be used with a standard electric drill. Always use lubrication (water), otherwise the diamond core drill will burn. Suitable for use in drill hole on glass, , tile or granite and so on. Color: silver Material: tungsten steel Use Tips: 1. add water for coolant and drill slowly. 2. drill at 45 Degree to surface and align to as hole forms. 3. Never use drills while machine is in hammer action. Model:Diamond Coated Core Drill Bit Outside diameter:60/80/100/120 mm, 2.36/3.15/3.94/4.72 inch Packing Include: 4 x Diamond Coated Drill Bits Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.