A ball valve is a device that contains a spherical closure unit that provides an on/off control of flow. The sphere typically comes equipped with a port known as a bore through its center. When the value is positioned correctly so that it aligns in the same direction as the pipeline, it is in an open position where fluid can readily flow through it. Pig valves are known for their reliability and bubble-tight sealing that can be an ideal choice for gas applications where a tight shutoff is absolutely necessary. The body of pig valves is typically made out of steel and can be made more durable with nickel plating. The most common ball valves are considered to be two-way, which allows for flow to travel linearly from the inlet to the exit without issue. Three-way and four-way valves allow for flow to travel in multiple directions, which include 90-degree angles.