Tungsten carbide insert bit ,TCI bit,button bit 1,Sizes range from 3 7/8" to 26" . ... 2,Reliable bearing and lubrication system 1.Cutting structureThe durability of premium tungsten carbide insert is improved ... applications.5. 5.Current Main Availability Diameter/InchIADC CODE3 1/2 211, 121, 241, 537….3 7/8 131 ... , 537, 517….6 211, 121, 241, 537…. 12 1/2 211, 121, 241, 537….14 3/4 131, 211 ...