Ruskin parallel and opposed-blade HVAC control dampers are custom made-to-order. The damper frames are made of galvanized steel in a channel frame construction, offering an equivalent 13-gauge metal strength. The CD40 Series has 6" wide V-groove blades that are made of 16-gauge galvanized steel with synthetic bearings. The CD50 has aluminum airfoil blades with synthetic bearings. CD60 dampers offer 14-gauge blades.CD44 Basic control damper, approximately 4% leakage CD45 Standard control damper, AMCA Class 3 CD46 Low leakage control damper, AMCA Class 2 CD50 Aluminum frame air foil, ultra-low AMCA Class 1A CD60 Steel air foil, ultra-low AMCA Class 1A