... 1/4",17 1/2", etc. IADC Code:4-- Series, 5-- Series, 6-- Series,etc. Elastomer sealed bearing TCI BitCutting StructureThe durability of premium ... 3/4",17 1/2", etc. IADC Code:4-- Series, 5-- Series, 6-- Series,etc. Air Cooling Roller Bearing TCI BitCutting Structure The ... 5/8",12 1/4", etc. IADC Code:5-- Series,6-- Series,7-- Non-Sealed Roller Bearing BitCutting StructureThe durability of premium ...