Instruction: Answer the given question by extracting information from the supporting document.

Input:
Question: Does this hard drive come cased or will I need to buy an enclosure prior to installing? Thanks.
Document: This drive is perfect, will purchase more when the need arises in the future. Perfect for the application. Come quickly too.
I bought this to replace and older hd and put that one in the Sabrent SATA hd enclosure. I've ordered another enclosure to use for this drive as I now plan to buy a SSD to replace this one and it'll be another external drive as well.I bought this after reading the other reviews and it seems to be a great drive, especially for the low cost.
I only buy WD black drives. For the price performance and warranty, you cannot go wrong. I have used the WD warranty services many times and they always come through with fast courteous service. It is running smoothly in my file server with Dragonfly BSD installed on it.
Bought it as a replacement for my Laptop HD. NO problems with it. Great Buy. If u need a HD this is the one!
My current hard drive crashed so I took it to my IT guy and he found this on for me to get and put it in and it's been about a month and it's working just fine, no problems with the speed or anything else that I can see. So doing the job it's supposed to do.Thanks
This hard disk drive is serving my needs excellently. I had to replace the faulty Western Digital hard disk drive in my Dell XPS laptop computer. The only tool I needed was a Phillips size 00 screwdriver.After disconnecting the power cable and removing the battery from my laptop, I installed the new drive in my laptop and the old drive in an external enclosure.
I expect to get another 2 or 3 years of service out of this laptop.The drive I replaced was installed in a portable SATA enclosure, reformatted, and repurposed as a redundant back up drive. Since the old drive is no longer enduring the day-to-day wear of a system drive, it should last.If you have a hard drive nearing the end of its life expectancy, then I would recommend replacing it with a Western Digital drive.
There is no documentation included, so would only recommend to someone who has experience in installing a hard drive otherwise I would have given it a five. Purchased to clone the operating systems and programs on my old hard drive and install Win 8 in a multi boot configuration. Western Digital offers a free download program to clone their hard drives. You cannot upgrade from Win 8 to Win 8.1 if you install through usb connection.
The prior owner most likely got confused on how to handle a drive with advanced formatting, as they work a little bit different and seem to be pretty specific to windows 7 until you reformat them. This drive would not align with the Acronis cloning software the WD gives you for free when you buy their drives....  Any drive!! That it in itself is nice perk, as long as you can get the drive to align.
I ordered the WD 750 gb Black SATA III 7200 rpm drive to replace the dying 250 gb, 5400-rpm hard drive in my Macbook Pro A1260. I also bought the Vantec NexStar TX enclosure so I could connect it as an external drive and clone my original drive with Carbon Copy Cloner. I followed the iFixit guide for replacing my hard drive. Although I find that DIY projects are often more difficult than I anticipated, this project went exactly as advertised. My machine is noticeably faster.
Answer: It's a laptop HDD ready to install.  If you intend to use it as an external you need to/could buy an enclosure.