Forbes Marshall Piston Actuated Valves are 2-port pneumatically actuated OnOff valves for use on steam, water, air, oil and gases. A pneumatic signal acts on the actuator piston to open or close the valve with a spring return action. The valve plug has a PTFE soft seal to provide a tight shut off. Forbes Marshall Piston Actuated Valves are available in Normally Open, Normally Closed and Bi-directional Normally Closed configuration.