The TowerRAID TR4U is a selectable hardware JBOD or spanning enclosure that utilizes the widely available USB 2.0 interface for storage expansion. Designed with easy installation in mind, the trayless TR4U allows instant installation by simply inserting the hard drive after opening the protective ventilating cover. The new environmental friendly Auto-Power Synchronization design allows the unit to be powered on only when needed. The TR4U supports JBOD mode, which allows the computer to see individual hard drive separately. It also supports Spanning mode, which presents multiples hard drives as one combined drive. Having two different storage options makes the TR4U an effective way to expand storage using USB 2.0.