HP ProLiant 2.5″ SAS / SATA G5 G6 G7 Server Hard Drive Caddy, is a special casing for a hard drive or SSD. HP ProLiant 2.5″ SAS / SATA G5 G6 G7 Server Hard Drive Caddy is built from aluminum. Within the casing there is a plastic frame. Where you can mount a single 2.5 inch hard drive or SSD. Then inside this frame there is an adapter that connects the hard drive or SSD with the connector inside your server.