... of premium tungsten carbide insert is improved with new formulas and new techniques and new techniques ... . 2.Gauge StructureGauge protection with gauge inserts on the gauge surface of the ... 537, 517….6 211, 121, 241, 537….……….. ………………………………12 1/2 211, 121, 241, 537….14 3/4 131 ... ….………..………………………………26 131, 211, 537, 517…. API standard 12 1/4''steel tooth tricone bi for water well or ...