I got a SSD 2,5 OCY Vertex 120gb i wonder if this adapter http://images.webhallen.com/product/66429 should fit in iMac 27"?
You need a 3.5" to 2.5" adapter. Also, one side of the Apple HDD mount uses two pins that are threaded on one side and slide into mounting points within the chassis that are not removable. The mounting points have rubber grommets that the pins slip into. Then there is a single sided bracket that attaches to the HDD and then attaches with two screws to the chassis mount points with more rubber grommets as well.
Most HDD brackets do not have threads as the screws thread into the drive and hold the bracket in place. So, the pins will not easily attach to a typical bracket. And because you are using a 2.5" drive the screws that hold the bracket in place do not actually attach to the drive itself.
I did not know any of this going into the modification but I wanted to add 2 SSD's in the single HDD bay and saw THIS BRACKET posted somewhere. It holds two 2.5" SSD drives and is made of plastic. One thing I found out the hard way though is, if you do add two SSD drives the top drive sticks up too high to allow the LCD panel to lay flat when remounting the panel. Since the bracket is plastic it can easily be modified by drilling new holes. So I moved the mounting holes down on both sides to lower the overall height as much as possible. This also allows the threaded mounting pins to screw into the plastic bracket very nicely.
Now I have two Corsair Force 120's mounted in the 3.5" HDD bay. The dual SSD RAID0 Xbench numbers are pretty amazing. I had to revert to using a single drive for booting though because I need to run Bootcamp and could not get that to work with OSX Software RAID0 boot drive.
The RAID0 boot drive was so nice I am now tempted to replace the optical drive with an SSD dedicated for my Bootcamp/Windows drive so I can go back to having RAID0 for the OSX boot drive. No, I don't need any of this stuff it's just for fun.