Today Amazon is offering the Sabrent USB 3.0 to SATA External Hard Drive Lay-Flat Docking Station for only $19.99. That's 50% off its $40 MSRP (although we usually see it for around $30) and definitely an awesome price for a very practical accessory to keep around. It has over 30,000 reviews on Amazon with a solid 4.4/5 rating and I actually own one of these myself and recommend it.
Sabrent USB 3.0-SATA External Hard Drive Dock for $19.99
The Sabrent USB 3.0 to SATA external hard drive accepts both 3.5" and 2.5" SATA hard drives and SSDs, although it's clearly designed specifically for 3.5" hard drives. There's no need to fiddle with the connectors every time you disconnect and reconnect the drive; you simply drop it into the cradle and you're done. There's also a cover that protects the drive although you might want to leave it open whenever you're taxing it for better heat dissipation. The USB 3.0 interface supports a theoretical max of 6Gbps (or approximately 625MB/s) although we all know that real world speeds are lower than that. Still, it's a huge upgrade from the 125MB/s max you get with USB 2.0 docking stations.
The external hard drive dock is plug and play with Windows, which means there are no additional drivers required. There is also a handy on/off switch so you don't need to worry about phantom power drain when it's not being used. Got internal drives lying around? You can effectively turn any internal hard drive into an external hard drive. For my particular use case, I use this dock as a quick way to grab files off a hard drive that's not installed in my rig. It's a lot faster than opening up my side panel to access an SATA plug. The package includes a USB 3.0 cable and Acronis True Image cloning software.
If you already have an internal hard drive, docks are a great alternative to buying a new external hard drive. Otherwise it's easier simply to just buy one of the many excellent external hard drives available.
