Hello there. From my point of view as a newcomer to this hobby, the way I look at it is when checking out leather I always think of thickness in preferably metric or inches, it's about thickness after all, just because a certain weight has some sort of equivalency to thickness it is not absolute nor easy to visualize it. I think that we still need to visualize the thicknesses in our brains and convert them into mm or fraction of inches, so why not just say and mark them in mm or inches. Gold and Silver and everything else we measure in wights and carats and not by its atomic weight even though each material can be measured by a different scale and way of measuring...