These conflat Viton gaskets fit a conflat flange size of 6.75 inches. They have been pre-baked and degassed to limit the outgassing in your vacuum system. Conflat (CF) flanges are used for ultra-high vacuum applications. CF Conflat flanges can be sealed with a Copper, Silver Plated Copper or Viton Gasket Seal. These Viton Gaskets are pressed into the knife-edge flange to achieve the high vacuum seal and can operate down to 10-13 torr (10-11 Pa) and can be heated to 450 °C for bake-out. North American flange sizes are given by flange outer diameter in inches: 1.33" ("mini conflat"), 2.125", 2.75", 3.375", 4.50", 4.625", 6.00", 6.75", 8.00", 10.00", 12.00", 13.125", 14.00", and 16.50". In Europe and Asia, sizes are given by tube inner diameter in millimeters: DN16, DN40, DN63, DN100, DN160, DN200, DN250.