I purchased this separately at the same time as buying my first SSD because it was much cheaper than buying an SSD with a 'laptop kit' (the transfer software can also be downloaded without cost).
I used it to connect my old Toshiba R500 Portege to a shiny new Crucial M4 SSD and it plugged into the SSD without problem, and the subsequent data transfer went without hitch (although the SSD itself locked down into 'safety mode', but that's another story). As is described on the item, after you've ripped out your old drive, you can store it in this box and use as an external USB drive if necessary.
Buy once, use forever. Recommended.