... 1,Structure features:1. Rolling seal bearing structure, cylindrical roller cone in slots in the body, increasing the shaft neck size.2 ... for bearing system provides good lubrication guarantee.4. Steel ball lock die, suitable for the high speed.5 ... 4,Certificate:5,we can provide more size Steel tooth(IADC)111, 121,131117,124,126,127 ... more good advance!!! API&ISO 8 1/2" kingdream Steel tooth tricone bit