Compact, 25 ga galvanized steel, attaches easily to wall or ceiling joists|Double strength mounting flanges with keyhole slots|Removable wiring cover make connections away from tight corners|No electrical knockout to remove|Polymeric duct fitting with tapered sleeve for easy, positive duct connection|2 x 4 in minimum construction space required|7-1/4 in L x 7-1/2 in W x 3-5/8 in H housing|Wall or ceiling installation|3 in duct size|For 1670F, 1671F, 1688F and 1689F