When you need to “dial in” branch air flow, Ruskin Model VFBD35 Value Flo “IRIS” Balancing Damper is well suited for ease of installation and labor savings. The unit has encapsulated iris segmented blades and integral air pressure taps for great flow control and validation. The calibrated locking hand quadrant is coordinated with specific aperture positioning. The aperture setting of the blades coincide with the P.A.M.S. (Pressure Across Monitoring Station) chart that is conveniently located on the damper. The product delivers instant calibrated cfm information to expedite the balancing process. An optional transducer may be ordered if constant validation of the flow is required.