A sight glass fittings, also called a sight window or view port, comprises two flanges, bolted together, surrounding a glass disc sealed with gaskets and provides a means of viewing the inside of a process vessel or tank. Typically used to visually verify stages of a process, inspect process media, and to observe liquid levels. Common applications include the viewing of internals of pressure vessels, tanks, silos, stirred vessels, separators pipelines etc. In addition to the sight glasses.