I bought the Leupold Mark 4 rings (steel, matte black, super high) to mount a Leupold 3-9x40 Mark AR scope on my Rock River Arms Standard A4 rifle. Installation was a breeze, and the result is a rock-solid, ultra-stable mount for the scope.
Milled from solid steel, the rings are very heavy and add appreciable weight to the rifle. The aluminum version would probably have been a better choice, but I'm still happy with the results.
Despite the high cost, these rings provide the ultimate in mounting stability, which is A Very Good Thing in my book.
Pros: Superb stability, easy to install
Cons: Very heavy, high cost
This review was written in the old system and had content requirements that are different than reviews written today.