... 4. Good feedback of clients 17 1/2" tricone drill bit : size from 60mm to 26 inch,metal ... with new formulas and new techniques for insert bit. Gauge StructureMultiple gauge protection with gauge trimmers ... Size: 6",6 1/2",7 1/2",8 1/2",9 1/2",9 5/8",9 7 ... with new formulas and new techniques for insert bit. Bearing StructureNon-sealed roller bearing. Drilling ... /4",6",6 1/2",7 1/2",8 1/2",9 1/2",9 5/8",9 ...