Fire Rated Recessed Light Enclosure: The FN-Z-15-16-9 accommodates most Compact Fluorescent (CFL) down lighting. CFL fixtures typically have housings that are larger in width and length than conventional incandescents. It measures 15.20" Wide x 16.20" Long x 9.50" Deep. Installs in floor/ceiling assemblies with joist spacing of either 19.20" or 24" o.c.