61FBL-24×24 (20×20 Neck) Filter Louvered Grille 61FBL-24x24 (20x20 Neck) Filter Louvered Grille 61FBL-24×24 (20×20 Neck) Filter Louvered Grille Category: Air Distribution Sub-Category: Returns/Grilles Next Product CURB-SEISMIC-16.5