Viewport, vacuum access door with a 4.50 CF flange mount, and a 2.56 center bore is fitted with a standard 7056 Borosilicate glass window. Flange has eight (8) clearance holes (for 5/16 diameter bolts) counter-bored into CF flange/door interface . Door assembly is fitted with a robust and adjustable dual-axis hinge, and a fast-acting, over-center latching mechanism that can be secured with included R-clip cotter pin. A Viton elastomer O-ring gasket is also provided. Access doors ship with a standard 195° swing-angle, however an optional 120° swing-angle Door-Stop kit is available for retrofitting hinge mechanism (purchased separately).