Below is a list of Sight Glass manufacturers from St. Louis, Missouri. Sight glass is used in industrial plants and machines in order to visually observe and monitor liquid and material levels, colors, flows or direction. It can be installed as the windows of a piping system, an external vacuum tube, or as a component with a frame screwed between two metal pipes. Tanks, boilers, reactors or vessels may contain components of sight glass in the form of liquid level gauges or inline sight points. Further uses include media vessels in chemical plants and in other industrial settings such as breweries, bio gas plants, pharmaceutical, food processing and beverage.