... ",9 5/8",9 7/8",12 1/4",17 1/2", etc. IADC Code:4-- Series, 5-- Series, 6-- Series,etc. 2. Elastomer ... 8",9 7/8",12 1/4",14 3/4",17 1/2", etc. IADC Code:4-- Series, 5-- Series, 6-- Series,etc. 3 ... 5/8",12 1/4", etc. IADC Code:5-- Series,6-- Series,7-- 4,Non-Sealed Roller Bearing BitCutting StructureThe durability of premium ... 8",9 7/8",12 1/4",15",15 1/2",17 1/2", etc. IADC Code:5-- Series,6-- Series 17 1 ...