It is usually used as a return air grille .The return grille type is used for the exhaust and supply of large quantities of air with minor pressure loss in facilities such as offices, warehouses, shopping centers…. The return grille type is used for the exhaust of large quantities of air with minor pressure loss and as return grille for the equipment like fan-coil etc. Return grilles are suitable for all supply or return sidewall / Ceiling, floor and sill applications. High quality, extruded aluminum or sheet construction, clean lines and a continuous appearance make return grilles an excellent choice for architectural spaces.