The 3063 has a ribbed lining, so the mat is needed to keep "invisible" ridge-lines from forming in your negative that will show in the final print. The material I got was flexible vinyl like you would use for a cutting board. The original Jobo ones were clear, and had little button-type protrusions to keep the film in place. I've only seen pictures of them, never handled one - if you can find a NOS Jobo mat, they go for $200 +. If you are developing in D-76 or Rodinal or Xtol, you probably won't have an issue with the 3063 as-is, but pyro developers are notoriously prone to the ridgelines showing up in prints.