642 is pretty good stuff... 1-mil, comparable to Maxell 35-90. 632/642 is the music grade stuff in the 600 series. I use it with my Akai GX-77... home hi-fi use. You could use it on machines that recommend 1-mil tape like the 22-2, 388 or Fostex R8, but personally I prefer backcoated tape for multitracking and serious mastering. If you’ve ever used Scotch Dynarange 212 or Maxell UD 35-90, I’m sure you’d be happy with 642 in the same role.