Western Digital (WD) has begun shipping its first Thunderbolt equipped storage device in the form of the My Book Thunderbolt Duo. The device is a dual-drive unit available in 4 TB (2 x 2 TB) and 6 TB (2 x 3 TB) capacities and features dual Thunderbolt ports (and only dual Thunderbolt ports – there’s no USB to fall back on here) on the rear for daisy-chaining of up to six My Book Thunderbolt Duo drives or other Thunderbolt peripherals.

The My Book Thunderbolt Duo features a brushed aluminum exterior, which seems to be the default standard for the majority of Thunderbolt peripherals hitting the market. It offers RAID 0, 1 and JBOD mode (Just a Bunch of Disks), which allows each drive can be accessed directly as an independent drive – handy for users running Windows on a Mac with Boot Camp.

Aimed at Mac-based creative professionals dealing with large graphics, video, or music files, or just Mac users with a truckload of digital content that needs moving around in a hurry, the unit is compatible with Time Machine out of the box and comes formatted as HFS + Journaled for Mac. It measures 6.5 x 6.2 x 3.9-inches HxDxW (165 x 157 x 99 mm), with the 4 TB unit weighing 4.73 lb (2.15 kg) and the 6 TB unit weighing 4.98 lb (2.26 kg).

The 4 TB My Book Thunderbolt Duo is available now for US$599.99, while the 6 TB model sells for $699.99. A Thunderbolt cable will need to be bought separately.