Just add a drive and go! Ultras portable, stackable external hard drive enclosure features a USB 2.0 and E-SATA interface and supports 3.5-inch SATA HDDs. Thats right you can use one, or use more just stack them up! The Ultra 3.5-inch external hard drive enclosure supports Windows XP, 2000, ME and Mac 9.0 and above. Built-in 30 mm cooling fan keeps the drive running at maximum performance while protecting it from excess heat. This easy to use external hard drive enclosure is easy to use its hot swappable, Plug and Play. Lay it down, stand it or stack it! No matter how you use the Ultra portable, stackable enclosure, it will meet and exceed industry standards.