The Brodie International Model BV86 Two-Stage Piston Control Valve is a two-stage hydraulically actuated control valve designed to utilize the flow stream as the source of power. The BV86 is used with a positive displacement flowmeter with a mechanical preset counter to provide shock-free two-stage closure. Through the use of optional accessory pilots, mounted in series with the BV86 pilot, functions such as back pressure, pressure reducing, or rate of flow control can be obtained.