ExitGlo 50 Series Exit Only No Chevrons 7" Letters Alluminum Narrow Profile Glow Type: Lettering UL924 Listed   ExitGlo 50-D Series Detachable Chevrons 7" Letters Alluminum Narrow Profile Glow Type: Lettering UL924 Listed             Running Man Series 10 chevron & running man options  4" lettering on rigid ABS substrate Glow Type: Background MEA Listed   ExitGlo 50-D Framed View of sign in Red, Green and in blackout conditions. Custom framing colors are available upon request.       How They Work Photoluminescent exit signs that are UL924 listed have been through extensive testing and evaluation to earn the right to bear the UL logo. They are entirely powerless and work by absorbing and storing available ambient light, then in darkness they release this stored light in the form of a bright luminous glow that eliminates the need for electrical wiring and battery backups that electrical exit signs require. A UL924 listing requires exit signs to be legible for a minimum of 90 minutes at the maximum listed viewing distance of each sign. ExitGlo™ exit signs will save you money and recent testing results show they consistently outperform other more expensive or non UL924 compliant models.