... is improved with new formulas and new techniques for insert bit. Gauge StructureMultiple gauge protection with ... is improved with new formulas and new techniques for insert bit. Bearing StructureNon-sealed roller bearing. ... Drilling fluid can enter the bearing directly for cooling; Balls lock the cone which reduces ... ",6 1/2",7 1/2",8 1/2",9 1/2",9 5/8",9 7/8",12 1/4",15",15 1/2",17 1/2", etc ...