... service 4.adequate stocks,fast delivery 5.IADC 517 8 1/2" IADC 517 Kingdream hard rock drill bits HAS series for oil well 1 ... .7mm(8 3/8”),215.9mm(8 1/2”),222.2mm8 3/4”) 241.3(9 1/2”),244.4(9 5/8”),250.8(9 ... ”)311.1(12 1/4”),346.0 (13 5/8”),349.2(13 3/4”)374.6(14 3/4”)381(15”),393.7(15 1/2”),406.4 ... (16”)444.5(17 1/2”),508(20 ...