The HP ProBook 6555b Notebook Supports Single and Dual Drive Configurations. (One 2.5" Solid State Drive or Hard Drive in the Primary Bay and One 2.5" Solid State Drive or Hard Drive in the Upgrade Bay Cradle) Note: If installing the second 2.5" Drive in the upgrade bay cradle in replace of the optical drive, you will need the upgrade bay cradle p/n 613682-001. If replacing the 2.5" Hard Drive for a 2.5" Solid State Drive, remove the bracket from the Hard Drive and install it on the Solid State Drive.