These valves are used to start and stop fluid flow into hydraulic cylinders. The flow rate listed is the maximum allowed GPM (Gallons Per Minute) that can be put through a valve. Our monoblock valves have power beyond Capability (Power Beyond Adapter Sleeve is required SKU: P40G-PB), as well as the ability to operate as a closed-center valve (Closed-Center Plug Required SKU: P40G-CC).