Adding to Johnpf's fine note: if you happen to see disparity between what's written in the Poser manual in the material room section and what Bagginsbill has to say on the subject, distrust the manual and stick with Bagginsbill.
A lot of the erroneous shaders that you will find in the marketplace come from trusting developers following the manual.

Another thing that the recent efforts to export materials and Poser objects to LuxRender has revealed: a lot of what we do in terms of trying to achieve "realism" or physical accuracy or whatever you want to call making-an-object-look-like-what-it-is-supposed-to-represent is a kludge... an artifice. A cheat. A workaround. So, shaders developed for Poser/Firefly don't really work too well for other renderers.

Monterey/Mint21.x/Win10 - Blender3.x - PP11.3(cm) - Musescore3.6.2

Wir sind gewohnt, daß die Menschen verhöhnen was sie nicht verstehen
[it is clear that humans have contempt for that which they do not understand] 

Metaphor of Chooks