Below is a list of Mini Ball Valve manufacturers from West Chester, Pennsylvania. A mini ball valve is a type of sealing mechanism with very small dimensions. Ball valves contain a ball with a hole bored through it. The valve is open when the ball is positioned with the hole running the same direction of the pipes; this allows the fluid to flow freely through the valve. When the control lever, handle or wheel is turned 90°, the ball is rotated by a shaft called the stem, which places the hole perpendicular to the flow, completely blocking it.