The 439D-10AW from GE Security is a Fire Alarm Bells are specially designed for fire alarm applications. The gongs are made of selected alloy steel to give the loud, resonant tones necessary in fire alarm systems. Two gong sizes are available to overcome different ambient noise level. The Fire Alarm Bells are of the underdome type with heavy duty mechanisms. Each bell is supplied with a mounting plate that fits any standard single-gang opening. For weatherproof application GE Security offers an optional surface weatherproof back box. Refer to the Specification chart for applicability and cata-log number of the weatherproof back box for the respective bell. Full Cast Grid - Add Suffix “G” to Catalog Number.Example: 438DG-6N5.Note Cat. No 323G type bells are not UL Listed.