... system 3.long working experience commodity:12 1/4 tricone bit 1.material:carbide 2.various types for ... 1/8”),158.7mm(6 1/4”),161.9mm(6 3/8”),165.1mm(6 1/2”)190.5mm(7 1/ ... 2”),193.6mm(7 5/8”),200.0mm(7 7/8”)212.7mm( ... 8 3/8”),215.9mm(8 1/ ... 311216,217, 227TCI(IADC)415,435, 417,437515,525,535,545, 517,527,537,547615,625,635,,617 ...