The target drive can be the same size if you use the included software and the drive only has one partition. It needs a larger target drive if you use it as a stand alone device.
I’ve had one of these for years. Works pretty good as a standalone harddrive dock. Some harddrives just won’t work with it…not sure why. I have another USB harddrive cable that all of my ‘working’ harddrives work with. Had some issues with Windows 7 and 8+ with it. It would eject itself from Windows and no matter what you did, unplug…plug in…turn off…turn on…if you tried to use it with Windows again, it would not work. Would have to restart Windows to get it to work again. Yes, I reinstalled Windows to see if that was the issue…still happened. Not sure if I got a lemon or not…but like I said, works good as a harddrive dock.