... The quality is stable.We can offer a large range of drill bits to suite the changing geology encountered durig project, the ... contributes the engagement in R&D, manufacturing and international trade of precision steel tubes, and has more than 3500 tons’ ... 45#, 160Mn, 20GrMo, 35GrMo, 40Gr. The products have the characteristics of small-sized, heavy-wall thickness, high precision, inner or outer ...