... Air register,Double deflection supply air register) FSB-B series is the traditional supply air grille, which ... blades joint to the frame by spring;FSB-B has no removable heart frame, but blades of ... °, to get different air supply distance. FSB-B series products can work with Opposed Blade Damper to ... two models: double-layer (SB-B, SB-C) and single-layer (DB-B, DB-C). Generally, for double-layer products, ...