The Flow Control Valves (Speed Controllers) actually have two types, which usually make customers confused. We're trying to make it clear and tell customers how to choose correct flow control valves.
Flow control valves control flow in one direction, allowing free flow in the opposite direction, so there are two types:
1) Meter-out (Control-out)
Most general used type. The flow rate of air entering from the thread side can be controlled, whereas air entering from the tube side comes out from the thread side at the same flow rate (free flow). This type is commonly used to control the exhaust flow from an actuator.
2) Meter-in (Control-in)
The flow rate of air entering from the tube side can be controlled, whereas air entering from the thread side comes out from the tube side at the same (not controlled) flow rate. This kind of flow control valve is usually used to restrict the flow to an actuator.