Global Air Supplies EC Balancer gives the ability to fine tune Systemair EC fans. It let's to take control of maximum fan speeds of both intake and exhaust fans with the balancer. Precision control of the negative pressure within the grow room is simple with the balancer. Always set the outtake fan higher than the intake fan to stop positive pressure ever occurring in the grow room environment. Designed in Germany to work with Global Air Supplies EC fan controller.