Instruction: Given a question and the related document, and generate the answer to the question based on the information provided in the document.

Input:
Question: Do you need a separate power supply for this?
Document: Works as described in the descriptions. Easy to use, I didn't need to read any instruction manual. Doesn't require the AC power supply for 2.5&#34; SSD. Totally love this product.
Works great just as advertised. I haven't really used the 3.0 features yet but it works perfectly without power with 2.5 hard drives. I've also connected a Blu-Ray PC drive to my MacBook Pro without any problems. Keep in my mind you will need to use the power supply for DVD/Blu-Ray drives and 3.5 hard drives.
This adapter comes with an AC/DC adapter that will supply the 12V to drives that need it. If you have a drive that doesn't need 12V then it works on the USB bus power and you don't have to use the adapter. I can't speak to the reliability because I have only had it an hour. I can say it's very very fast. I tested it with a 50% full Constellation.2 7200 enterprise class drive which is 2.5 inch that requires the 12V SATA pin.
The cable is short, I assume to prevent power loss if the adapter isn't plugged in, and that's another problem. But as long as you can put up with all that, it's not a bad product. If you need something more robust, I would suggest getting a dedicated dock from Thermaltake.
If you have to use the power adapter it is a bit of a pain, however if you dont it works really well. I like it and would buy another if needed. I just don't like the power supply.
If you have to any external HDD manipulation, this just works. If you have USB 3.0 ports, you will appreciate the speed boost, but works well/is backwards compatible with USB 2.0 The external power supply is ideal for working from small or under powered laptops. Recommended for any tech support toolbox.
I bought it some months ago and still works great! Love it! I read a few reviews about the connector feeling flimsy but it feels good enough for me, now if you're going to start moving it around or hang the drive from the cable.... well.... that's going to feel flimsy.You only need the supplied power cord for 3.5 HDD, don't need it for 2.5 (laptop) drives or SSD.The cable is waaaay too short.
I tried to plug this device into various different hdd and ssd, and into two different computers, with both usb 2.0 and usb 3.0.In none of those scenarios did the product work, or computer recognize the drive. It could have been lack of power, but I used the power supply that was provided in the box.It seemed like a good idea, but it did not work as advertised.
I bought this handy little thing so I could plug an internal bluray drive into my laptop. Much cheaper then buying the external version and works just as well. This adapter comes with its own 12 volt power adapter, this was a good thing since my usb 3 ports couldn't supply enough power to open the tray! It works! I can't stress that one enough.
I love this gizmo. I use it for connecting a full-size LG Blu Ray burner to my mini-itx computer via USB 3 port. The SATA connection provides enough power for the drive to power on, but it needs the external (and included, thank you very much) power supply in order to read and/or write to a disk. While this adapter kit was a bit on the pricey side, it's utter simplicity and reliability makes the price justifiable.
Answer: The USB 3.0 bus provides enough power for most small laptop drives and SSDs, but larger desktop hard drives and optical drives will require the external AC Adaptor, which comes included with the device.