As a result of their reduced profile (2.19 inches wide and 1.18 inches high), the Power Sentry fluorescent battery packs can be used in tight applications, including low-profile lensed troffers and 3-inch louvered parabolic fixtures. Upon power interruption, the battery pack automatically operates a 2 to 4 inch or U-shaped T8 or a T12 fluorescent lamp at reduced light output for 90 minutes. They are compatible with electronic T8 and magnetic T12, instant start, rapid start, and slimline ballasts.