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