"Full tower cases" are typically or more in height and intended to stand on the floor. They can have anywhere from six to ten externally accessible drive bays. However as computing technology moves from floppy disks and CD-ROMs to large capacity hard drives, USB flash drives, and network-based solutions, today's full tower cases typically have only no, one, or two external bays for CD drives, with the internal bays moved elsewhere in the case to improve airflow. The full tower case was developed to house file servers which would typically be tasked with serving data from expensive CD-ROM databases that held more data than the hard drives commonly available. Hence many full tower cases include locking doors and other physical security features to prevent theft of the discs. Today, full tower cases are commonly used by enthusiasts as showpiece display cases with custom water cooling, lighting, and tempered glass (replacing acrylic). They may also hold two computers (as is the case with the Corsair 1000D) and dual power supplies (Corsair 900D).