These conflat copper conflat gaskets fit a conflat flange size of 2-3/4 inches. ConFlat (CF) flanges are used for ultra-high vacuum applications. These fittings use a copper gasket and knife-edge flanges 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: 1-1/3 ("mini conflat"), 2¾, 4½, 6, 8, 10, 12, 13¼, 14 and 16½ , in Europe and Asia, sizes are given by tube inner diameter in millimeters: DN16, DN40, DN63, DN100, DN160, DN200, DN250. These vacuum fittings are made of corrosive resistant stainless steel.