Does what it says on the tin - at least it did for my Late 2011 MacBookPro 13". I put original hard disk into it and system saw it straight away, taking superdrive completely out. However, its bit overpriced as for this volume of plastic and bit of metal. Also, it is lacking of any type of handles that you could use to screw it in place. Effectively, you just slot hdd in it, connect it to motherboard in place of superdrive and put the cover on top of it. Thats it. Bit worrying that it may start wobble without being firmly screwed in. The bit of plastic that you put behind hard disk once this one is positioned into caddy is also bit flimsy. Again, it does the job but could do with few simple improvements.