Western Digital My Book 4TB USB 3.0 External Hard Drive

Features
Dual USB 3.0 and USB 2.0 Interface - A single drive with universal compatibility today and next-generation speed for tomorrow. Use it with USB 2.0 now and step up to USB 3.0 speed when you're ready.
Up to 3x faster transfer rates - When connected to a SuperSpeed USB 3.0 port this drive lets you access and save files up to 3 times faster than USB 2.0. Transfer a 2-hour HD movie in just 3 minutes instead of 13 minutes.
WD SmartWare software - You're in control of your backup. Install all the features, select just the components you need, or if you prefer, choose not to use the software at all.
Automatic, continuous backup - Works quietly in the background to protect your data using minimal PC resources. Whenever you add or change a file it's instantly backed up.
Password protection for privacy - Gain peace of mind knowing that your data is protected from unauthorized access with password protection and encryption.

Specifications
Data transfer rate: 480 Mb/s (maximum) in USB 2.0 mode and 5 Gb/s (maximum) in USB 3.0 mode
Interface: USB 3.0 and 2.0
Compatibility: Formatted NTFS, Windows XP, Windows Vista, Windows 7 / Mac OS Leopard or Snow Leopard (Requires re-formatting and will work in USB 2.0 mode)
Dimensions (LxWxH): 6.5 x 5.3 x 1.9 in.
Weight: 2.6 lbs.