HPE Hot-Plug /, Redundant - Plug-in Module 500 Power Supply 720478-B21, Silver Hp Flexible slot power supplies provide up to 96% power efficiency with 80Plus platinum-certified power supplies that lower server power requirements and reduce power waste in your data center Hp Flexible slot battery backup option is an HP innovation to provide 750W of battery power up to 60 seconds with Flex slot Form Factor Specification compliance: Flex slot