【Drill Bit】These diamond drill bits are made of industrial grade carbon steel. Fine workmanship and super wear-resistant, sharp. 【High Quality Drill】Each hole is treated with smooth and accurate surface treatment,and the top oh the hole is thickened to achieve excellent cutting strength. 【 Hole Saw Sizes】6-customize,to meet various demands 【Wide Usage】Used on Drill Glass,Wood,Tile Bottles,Blocks Jars, Ceramic,Slate Mable, Granite Light Stone, and other hard surfaces.