... the near future 1,Structure features:1) Material: 15CrNi4MO2) Rubber/metal sealed bearing3) Jeurnal/rock bearing 4) Cutting element:hard alloy cutting ... tooth5) Apply to soft-medium,medium-hard drilling information 6) Bit size:8 1/2"IADC ... ,127mm(5”)130.1mm(5 1/8”),133.3mm(5 1/4”),139.7mm(5 1/2”),142.8mm(5 5 ... 10 5/8”),295.3(11 5/8”)311.1(12 1/4”),346.0 (13 5/8”),349.2( ...