The actuator rotary actuator Type 2051 includes single-acting and double-acting pneumatic linear piston actuators with a universal mechanical interface in accordance with ISO 5211. The actuator stem is rotated through 90º by the pressure force of the pilot air or the force of the reset fields. The rotary movement can in turn be used to actuate corresponding proportional valves such as ball valves or butterfly valves. The rotary actuator can also be combined with the positioners from the 8791/8792/8793 series. The actuator can be equipped with the end position feedback boxes from the 1061 series for pure position monitoring.