PTFE resins are used in both grades of fabric.  They will withstand -100°F to +500°F.  The difference between the standard and premium grade is the amount of PTFE resins that is applied to the woven fabric.  The greater the thickness of PTFE the better the chemical resistance and higher electrical strength.  The texture of the premium is also smoother and provides a more lubricated surface.  The standard grade feels somewhat porous and allows better drainage.  Manufactured in the United States.