Ray, the NMRA standards for rail list "C", the railhead width dimension as .035 for Code 70. Code 125 is .063 and Code 148 is .066. There is no Code 140 listed in the NMRA standards. For info, the .138 tall rail used for SHS/MTH track, Lionel FasTrack and FVM track is .048, thinner than Code 125 rail even though slightly taller. I have some Code 125 rail on my layout and the MTH .138 track looks better because of the visibly narrower railhead. The MTH rail is the essentially the same width as Code 100, which is .045.