Features:* .* Perfect Application - This diamond coated core milling cutter removes complete circle from glass, marble, tile, granite, ceramic or others. They are ideal for drilling glass, tile bottles, jar blocks, porcelain ceramic fiberglass tile, mable slate, granite light stone* Super material-these diamond drill bits made of high-speed steel, which is and has a long service life, which are of and good performance, which is great for making clean and accurate holes.* Sharp and smooth cutting-coated with high-quality diamond, The diamond hole saw creates a precise, smooth cut with no broken edges. Reduced drilling speeds, low drilling pressure, and increased use of water lubrication significantly extend the life of the drill bit* Note-when using the diamond drill bit, use lubrication (water), otherwise the diamond drill bit will burn. Not for use on concrete or at depths greater than about 1/2". Specifications:Material:Steel10pcs 6-30mm:(6/8/10/12/14/16/18/20/22/30mm)Package Content:10pcs Diamond Drill Bit