Drill Bits Size: 10pcs of diamond drill bits kit each diameter of 1/4 inch (6mm) with round shank for drilling hole saw. Provide a variety of options for drilling, can meet your basic drilling needs Diamond Coating: The drill bits are made of high quality diamond by vacuum brazed diamond technology. Thicken diamond coated on the tops offers the ability that each sharp bit for more holes Inside Wax: Our diamond drill bit is integrated with wax lubricant inside for efficient drilling, which melts while dry drilling and cools the holing surface. The water can be used as additional cooling to prolong the life of the bit Speed & Smooth Cutting: Follow the use skills start drill at 45° angle to surface and align to 90° angle as hole forms. Can dip in water, no need for a constant water delivery system, for quick and easy use Recommended Machine: Corded Drill, Cordless Drill, Benchtop Drill. Use electric hand drill: Recommended speed not less than 1500-2000RPM. Faster the RPM, longer the drill bit's working life. Suitable for porcelain, ceramic, granite, marble, masonry, concrete, other types of tile. (Note: NOT for tempered glass, plastic and wood) Goldblatt 10pcs 1/4 inch Holesaw Kit Included: 6mm (1/4”) *10 vacuum brazed diamond core drill bits of different sizes to meet your various tiling work requirements.