... performance.Main Type AvailableSize: 5 7/8",6",6 1/2",7 1/2",7 7/8",8 1/2",9 1/2",9 5 ... /8",12 1/4",14 3/4",17 1/2", etc. IADC Code:4-- Series, 5-- Series, 6-- Series,etc. Air Cooling Roller ... ",9 5/8",9 7/8",10 5/8",12 1/4", etc. IADC Code:5-- Series,6-- Series,7-- Non-Sealed Roller Bearing BitCutting ... AvailableSize: 2 3/8",3",3 5/8:",3 7/8",4",4 1/2",4 5/8",4 3/4",6",6 1/2",7 ...