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