... inserts on the heel rows and inner rows. 2)This design provides a fast drilling rate and added cutting structure durability in ... .Main Type Available Size: 6",6 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 ... :",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 ...