1)ISO9001:2000 management system 2)More than 20 years manufacturing experiences Glass drill bitsThey are made of high-quality alloy structured steel with special grade carbide tip, and automatically brazed in the hear-treating furnace from Germany under the temperature of 1120 . Application: Concrete, Clinker, Masonry, Stone. Flute Available: "W" Flute, "U" Flute, "L" Flute.