Products Architectural Louvers, Dampers, Roof Curbs, Actuators, Grilles, Sunshades and more. Drop Plenum Diffusers - Drop Plenum Diffusers: Model:FFPD Flat Face Drop Diffuser/Plenum APPLICATION The model FFPD is a drop diffuser plenum that has flat faced double deflection grilles. This model can be custom built up to 100,000 cfm. FFPD DOCUMENTS - Submittal Sheet - FFPD Submittal (discontinued) - FFPD BIM (REVIT) Balancing / Regulating Dampers UV Products Iris Dampers Drop Plenum Diffusers Louvers Dampers UL Listed Dampers Roof Curbs and Rails Sunshades Architectural Grilles Ventilators Doors Actuators Fans Air Measuring Products VAV Terminals Security Bars & Grilles Plenums Duct Take-Offs Custom Work Manufacturer Cross Referencing System View Now Previous Next