A butterfly valve is a specialized type of flow control device that utilizes the principles of hydraulics and pneumatics to control the flow of liquids, gases, or other materials. This type of valve is well-suited for applications where space is at a premium and features an easy-to-operate, lightweight construction. The official business definition of an indicating butterfly valve is: an industrial component consisting of a quarter turn disc mounted on top of a stem which, when opened, allows material to flow through a series of interconnected piping systems. The stem is connected to a handle that is used to open or close the valve, while an indicator pin gives visual feedback as to the valves position.