... 1/2",7 1/2",8 1/2",9 1/2",9 5/8",9 7/8",12 1/4",17 1/2", etc. IADC Code:4-- Series, 5-- Series, 6-- Series,etc. 2 ... : 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 1/2",8 1/2",9 1/2 ... ",9 5/8",9 7/8",12 1/4",15",15 1/2",17 1/2 ... ", etc. IADC Code:5-- Series,6-- Series 17 1/2 ...