... shirttail increases gauge holding capability. 3.Bearing Structure Air cooling roller bearing package. Balls lock the cone,which reduces ... -dropping to minimum. 4.Product ApplicationIt is suitable for mining applications. 5.Current Main Availability Diameter/InchIADC CODE3 ... , 537….………..………………………………26 131, 211, 537, 517…. API standard 12 1/4''steel tooth tricone bi for water well or oil well drillng