It's made from rolled or forged AISI4145H chrome-molybdenum steel. The content of chemical composition and microelement is controlled effectively throughout the whole process. According to its different figures and materials, it can be divides into three types:

Type A columnar made from ordinary alloy steel, both inside and outside of the cross section of the pipe are cycloidal

Type B spiral made from ordinary alloy steel, with a spiral chute on the outer surface of the pipe

Type C non-magnetic made from stainless alloy-steel of low magnetic permeability, both inside and outside of the cross section of the pipe are rounded.