... 7/8",12 1/4",17 1/2", etc. IADC Code:4-- Series, 5-- Series, 6-- Series,etc. Elastomer sealed bearing ... 1/4",14 3/4",17 1/2", etc. IADC Code:4-- Series, 5-- Series, 6-- Series,etc. Air Cooling Roller ... 7/8",10 5/8",12 1/4", etc. IADC Code:5-- Series,6-- Series,7-- Non-Sealed Roller Bearing BitCutting ... /4",15",15 1/2",17 1/2", etc. IADC Code:5-- Series,6-- Series 8 1/2" Brawny IADC 517 ...