The ECOQUIP Series 9000-6 Pump Jack System provides increased lifting capacity and a greater stroke length over previous ECOQUIP 9000 series pump jacks. Like it's predecessors, the design is based on fluid displacement principles and it operates much like the braking system on an automobile where a master cylinder displaces fluid to the wheel cylinders. Gas ballast stores energy during the pump down stroke and serves to balance the unit. Balancing is done by adjusting the ballast pressure while the unit is operating. Maximum energy is a available when the rod load is highest.