... 4. Good feedback of clients IADC 517 537 8 1/2" tricone bit : size from 60mm ... /2",9 5/8",9 7/8",12 1/4",17 1/2", etc. IADC Code:4-- Series, ... 8",8 1/2",9 1/2",9 5/8",9 7/8",12 1/4",14 3/4",17 1/2", etc. IADC Code ... /2",9 5/8",9 7/8",10 5/8",12 1/4", etc. IADC Code:5-- Series,6 ... /8",9 7/8",12 1/4",15",15 1/2",17 1/2", etc. IADC Code: ... 5-- Series,6-- Series IADC 517 537 8 1/2" tricone bit ...