Quickly connect an external 2.5" hard drive or solid state drive to a USB 3.0 port. The power supply allows you to rotate drives (probably even 3.5" drives, haven't tried them yet) to connect. Much more practical than a docking station. Allows booting from an external drive (plugged into this thing) in OSX 10.6 to 10.11 by holding down the select key at startup.