... 1.Tungsten carbide insert bit, TCI bit, button bit 2.Sizes range from 3 7/8" to 26 ... new formulas and new techniques and new techniques. 2. Gauge StructureGauge protection with gauge inserts on the ... . 5. Current Main Availability Diameter/InchIADC CODE3 1/2 211, 121, 241, 537….3 7/8 131 ... 2 131, 211, 537, 517….18 1/2 211, 121, 241, 537….………..………………………………26 131, 211, 537, 517…. tungsten carbide drill bits ...