APC Smart-UPS X 120V External Battery Pack Rack/Tower Hot-swappable batteries: Ensures clean, uninterrupted power to protected equipment while batteries are being replaced Rack/Tower convertible: Protects the initial investment in the UPS when migrating from tower to rack-mount environment Scalable runtime: Allows additional run time to be quickly added as needed Operating temperature: 32 - 104 F ( 0 - 40 C ). User-replaceable batteries (APCRBC143) Compatible with 4U Server Racks. Operating Relative Humidity : 0 - 95 percentage