... 2", 9 5/8",9 7/8",12 1/4",15 1/2”,17 1/2",22”,24”,26” ... etc.IADC Code:4-- Series, 5-- Series, 6-- Series, etc.Drilling hours ... new formulas and new techniques for insert bit4. Gauge structure: Multiple gauge protection with trimmers on the heel of cone, ... carbide inserts and hard facing on the shirttail increases gauge holding capability and bearing life5. Seal and Lubrication: ...