These 6-Way Cube vacuum fittings are CF 2.75 inch, 2 3/4 inch (CF) bored through 6 hole flanges. 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 1x10-10 torr 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"), 2-3/4, 3-1/3, 4-1/2, 6, 8, 10, 12, 13-1/4, 14 and 16-1/2 inches. In Europe and Asia, sizes are given by tube inner diameter in millimeters: CF16, CF35, CF50, CF63, CF100, CF150, CF200, CF250. These vacuum fittings are made of corrosive resistant stainless steel.