The Model PRD-RD pressure regulating dampers are a single blade round barometric damper assembly constructed from 24 gauge galvanized steel, with a counter balanced weighted arm. This is the simplest, most economical way of bypassing excess static pressure in multi-zone applications. Resistance is controlled by offsetting the arm and adjusting the weights. The arm can be inserted into either side of the damper for added versatility. The PRD-RD bypass damper is an effective By-Pass solution for any Constant Speed or Variable Speed Zoned HVAC system up to 4 ton capacity.