... mutual benefit, provides the highest quality products and attentive service for our customers". We are looking forward to establishing relationships with ... welling drilling and so on.3.It is almost suitable for hard rocks, such as limestone, dolomite, chert, firm sandstone, and ... /8”)269.8(10 5/8”),295.3(11 5/8”)311.1(12 1/4”),346.0 (13 5/8”),349.2(13 ...