The 815101-B21 is an HPE Ethernet 10Gb 2-port 562FLR-SFP+ Adapter, a network adapter designed for HPE ProLiant servers. It provides two SFP+ ports, enabling high-speed 10 Gigabit Ethernet connectivity, and its FlexibleLOM form factor allows for seamless integration into compatible servers, making it suitable for demanding network environments requiring high bandwidth and low latency.