It is a stand alone dual bay docking station. I used it once to copy a security system 2T HD to another. Both were the same capacity. I am not that concerned with transfer speed but more with plug and play. I also have a laptop HD that i could not use in the past which fits in this dual dock.
Works well for the ( hopefully few times) i need to use it

When my IOCREST USB to Sata docking device choked on a couple of drives it was clear that it was time to find a replacement. As soon as the USB 3 and power were connected to the WavLink the first drive checked was the one with the valuable data stored on it--but wasn't accessible with the IOCrest.

Right out of the box the WavLink worked like a champ, immediately opening Windows 10 File Explorer.

The Wavlink is aces in my book.

It works. It's not as quick as copying over like some are, but it does work. Only drawback is your destination drive has to be bigger than your original drive. If it's even the exact same size the copy won't work, your destination has to be bigger even by a little. My 500gb wouldn't work to another 500gb, so I tried a 512gb drive and it did work- so make sure your destination drive is bigger. If it was even faster I'd give it a 5, but the fact that it's slower than other brands, I give it a 4, still worth it though.

Great product! Instant storage expansion for my PC using some old drives I had laying around. Five minutes after receiving the unit, it was up and running in my workshop. Works exactly as advertised, not to mention that WavLink has a great product warranty (not that I will need it). Oh yeah, and the price is right!

WAVLINK USB 3.0 to SATA (5Gbps) Dual-Bay Hard Drive Docking Station For 2.5 inch/3.5 Inch HDD,SSD Support Offline Clone / Backup /UASP Functions [8TB×2 ]-Black

The docking function works well enough, appears to operate at full USB 3.0 speed, but the original unit's disk clone function failed to work out of the box after repeated trials. The included manual was little help, and the vendor's website had no useful information. Returned the WAVLINK unit the day after receiving it.

The vendor, WAVLINK, then contacted me through Amazon, and asked to send a new unit for me to re-retry the disk cloning function. I received the unit and once again attempted to clone a clone a 1TB (WD Blue) disk to a 2TB (Seagate FireCuda) disk. They were very clear that the following directions had to be followed in order:

"Hard Drive Duplicator Function:
Don't plug USB to a computer when using the Clone function. Ensure the Target HDD is the same capacity of the Source HDD or larger.
1, Ensure the Power Switch on the rear is in the OFF Position and plugged in properly.
2, Insert the Source HDD in the rear near the power plug and insert the Target HDD in the front.
3, Power on the Dock and wait until the blue lights labeled Source and Target on the front of the unit are both on solid.
4, Press the button until both the blue Source and Target HDD lights flash. Then release the button. (Cloning is now ready) 5, Press the button again to start the cloning process. The progress will be shown on the front panel.
6, When all the progress lights turn off the cloning process is complete.
7, Turn off the power button and then remove the drives.

Note:
The new drives need one more step to make the drive useable.
First open disk management--> on the bottom select the partition that is called unallocated partition---> right click the unallocated partition and click extended volume and follow the procedure and remember to select the volume format as NTFS."

(This information was also presented in another review, and was the process I originally followed.) I followed the WAVLINK directions with the new unit and it worked as advertised. The clone function worked well, worked quickly, and kept me informed through the front panel lights as to its progress. All of the testing I have done indicates that the data on the 2TB Firecuda is an exact copy of the 1TB WD Blue disk, with an additional partition that needed to be activated via Win10's disk manager. Based on my experience I can only assume that the original unit was electrically defective, or had faulty firmware. The new unit simply worked as advertised.

I do not know how it will work over time, but the unit sent by WAVLINK appears very solid. I recommend the unit.