Butterfly Valves is a valve, which can be used for isolating or regulating flow. The closing mechanism takes the form of a disk. Operation is similar to that of a ball valve, which allows for quick shut off. These valves are generally favored because they are lower in cost to other valve designs as well as being lighter in weight, meaning less support is required. The butterfly is a metal disc mounted on a rod. When the valve is closed, the disc is turned so that it completely blocks off the passageway.