Like the Duo Docks of yore, the Apricorn Aegis NetDock facilitates enhanced desktop mode functionality while retaining an ultralight's easy-to-carry portability when it's untethered. the NetDock is an external hard drive, a four–port, self–powered USB 2.0 hub, and in addition has a trade–loading optical CD/DVD burner/player drive, making it especially well-suited as a companion peripheral for the optical drive-less MacBook Air or many PC netbooks