Habonim patent innovative four-piston scotch-yoke design combines the benefits of high-power scotch-yoke mechanism to generate maximal power and high Start and End torques, where most valves require it and the balance and compactivity of the four-piston mechanism to provide fast and efficient operation with minimal maintenance. The patent four-piston scotch-yoke pneumatic actuator provides almost 100% higher power-to-size ratio. In other words, a comparable traditional high-torque scotch-yoke actuator will be twice as big as a Power CompAct unit. The Power CompAct unit is much faster in opening and closing and uses less compressed air to operate. The evenly balanced forces of the four pistons and short travel (short piston) provides un-matching high cycle long life without maintenance for hundreds of thousands of operations.