This winch line product name is "speedline". It is well-known as Pentagon Line, which reduces airodynamical drug because of its Pentagon cross section. The rationale is that non smooth surface can create a turbulant boundary layer intentionaly in order to avoid the boundary layer from burbling. , whose cross section is Pentagon. It is well-known that there occur great drug force if the boundary layer burbles. Because turbulant boundary lay is hard to be burbled, Pentagon cross section may result in suppressing drug force arround the winch line surface over the various fruid profile.