Leave it to Dell! I push OptiPlex 3010 desktops. On quite a few occasions I get requests to put in a SSD as the primary drive and move the platter hard drive to the secondary position. Usually not a big deal but Dell tries to shave every possible cent on manufacturing and it does cause problems.
I also use Intel 530 Series SSDs. The come with a 2.5" to 3.5" adapter but (as with pretty much anybody's 2.5" to 3.5" adapter) the 2.5" drive is mounted dead center in the middle of the adapter so if you compare the data connector and power connector to an actual 3.5" sata drive the are shifted to the center about a half inch. Dell in all their infinite wisdom doesn't give you a half inch play between the first sata power connector and the second sata power connector so you can put the power connector on the second drive without really, really stretching it to the point it might break.
So what I am actually looking for is a 2.5" to 3.5" mounting kit that will leave the data and power connectors in the exact same place and position as on a true 3.5" sata hard drive.
Another application that might make more sense is a mounting kit that will let you put a 2.5" hard drive in a raid 3.5" hard drive slot, hot swap.