Diamond drill bits 1, Diamond grits are producing by ourself, which can guarantee the quality always best. 2, two types quality for your choose. the one is more sharpness, only 3-4 minutes to drill, can drill the holes about 1000 pcs. the other is well wear-resisting, need 6-7 minuts to drill, can drill about 2000 holes. 3, 28 years producing experience and professional guidance,will cut your cost and engry.