USAIRE 26.6-in x 24-in Steel White Sidewall/Ceiling Filter Grille
Grille – a series of deflectors in the shape of blades or fins fixed in a frame to allow air to pass through from duct to room space
Register – a grille attached with a damper or valve to control the air flow volume
Diffuser – a unit with duct connecting piece and a larger face piece with multiple blades to spread out air flow to multiple directions. Examples are drop ceiling T-bar diffusers and round ceiling diffusers
