Can I put an SSD in this unit.
Can I put an ssd in this unit or does it only take hard drives only?
You should be able to put any 2.5" Serial ATA device into this. But, if you do put an SSD into it, you are restricting the speed at which the drive can get data to the computer. USB 3 is fast, but not as fast as an SSD plugged directly into the Serial ATA bus of your computer.