Battery Back-Up; Nickel-Cadmium battery (4.8V 300mA) delivers more than 3 hours capacity to emergency lamps. Recessed or surface, ceiling, wall and end mount installation. Steel housing and aluminum trim plate. Etched acrylic faceplate with clear background. Letters are 6" high with a 3/4" stroke; single or double face configuration.Green or red lettering, white or black housing. UL listed, indoor use only; meets UL924 and NFPA10.