These Quick Flange demountable vacuum fittings have a flange size of KF40, NW40 with a Uncoated Quartz Fused Silica viewport view diameter of 1.19 in and a glass thickness of 0.158". Demountable Viewports are used for ultra-high vacuum applications and molecular spectroscopy. These fittings use a Viton O-ring gasket, operate down to 10-8 torr (10-11 Pa), and have a max bakeout temperature of 150° C. The operable wavelength of the Uncoated Quartz is between 200nm to 2000nm. 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. At present we have the following demountable viewport sizes listed in the graphic below and have replacement viewport glass and O-rings for sale.