Seagate Expansion STKM4000400 external hard drive 4 TB Black

Amazon

Sleek and simple portable drive design for taking photos, movies, music and more on-the-go Drag-and-drop file saving USB 3.0 powered Automatic recognition of Windows and Mac computers for simple setup (reformatting required for use with Time Machine) Enjoy peace of mind with the included limited warranty and Rescue Data Recovery Services

Currys

Good to know- This Seagate portable hard drive doesn't need a power adapter - it powers through the USB cable, so you can use it anywhere- Since it's plug-and-play, you can just hook it up and you're good to go- If the unthinkable happens and the drive gets damaged, the Rescue Data Recovery Services will help you recover your data