... service 4. Good feedback of clients IADC 517 537 8 1/2" tricone bit : size from 60mm to 26 inch ... 7/8",12 1/4",17 1/2", etc. IADC Code:4-- Series, 5-- Series, 6-- Series,etc ... 1/4",14 3/4",17 1/2", etc. IADC Code:4-- Series, 5-- Series, 6-- Series,etc ... /8",10 5/8",12 1/4", etc. IADC Code:5-- Series,6-- Series,7-- 4,Non ... 1/2",17 1/2", etc. IADC Code:5-- Series,6-- Series IADC 517 537 8 1/2" tricone bit