Now I've looked at the image, I don't think you'd ever go for steel fittings on stainless pipe either... All the pipe I've seen listed as hydraulic has a working pressure and I seem to recall it's all about the same but dependant on the size of the pipe, the bigger it is the lower the swp.I have this feeling that whoever wrote that order is "badly informed". The term "hydraulic pipe" has no precise meaning. There is a heck of a difference between stainless steel and galvanised steel; I cannot believe a qualified person would have offered that option. A max working pressure would have been nice to have. These guys used to be good. Swagelok are expensive.