What's the difference between a SSD and a upgrate kit?

I believe the upgrade kit adds items that would allow you to use it in a laptop bay

I own 2 currently and waiting for prices to drop on Plextors M5Pro 256GB

So should I, for a desktop, get a upgrade kit or a regular SSD?

regular one - it's normally cheaper

does one have an adapter to let the SSD fit in a regular drive bay ( pc )

Dingo has it backwards, ssds are 2.5" which is laptop size so a laptop doesn't need anything extra. But desktops are 3.5" meaning they need an adapter and that is what an upgrade kit includes. It says in the the description btw. But an adapter is $5 so is actually cheaper to get the ssd alone and get an adapter.

Some does, like kingston hyperX, most does not. But you can get the adapter cheaply, like this

http://www.amazon.co.uk/StarTech-com-Universal-Mounting...

No need to pay the extra $$ for the unnecessary cable, ext USB box etc in a kit unless you really need them

So I have to get a upgrade kit/ SSD with adapter?

If your case has a spot for an ssd, then no. But if all you have is a 3.5" bay then yes if you want it mounted. I see in your other thread you were looking at the haf xm which has a 2.5" mount on the back but idk if you want it there or got that case.

^ explaind weel obove.
Bare drive - you get bare drive, noting else.
Kits - Can include the 2.5->3.5 inch mounting braket. May or may not need depending on case. On occassions, I've simply made my oun, bat as other explained - they are cheap. The othe item that may be included in the kit is a "cloning, or Migrating" software.
This is good if going from say a smaller SSD to Newer SSD or a larger SSD. When Moving from a HDD -> a SSD it is recomended to do a clean install.

PS This software is no Biggy as EasyUS is FREE and does a great job.

Best answer selected by SpaceMilk.