I originally bought this block for my 1 gig edition of the Sapphire 4850. It was a sinch to install as the screw holes lined up perfectly and I just applied AS5 and the included thermal tape on the directed parts.
My temps went from 50 degrees Celsius idle and 65 under load to 35 on my water setup idle and 39 under load
The bad news:
I loved it so much that when I bought the new version of the 1 gig sapphire, they changed the reference of the card and this no longer fits (Thus the reason the Sapphire card is now under the non compatible list.)
Danger Den easily helped me out to return the unused block and I've had a pleasant experience all around!