The top portion of the rings have to be "snapped" onto the scope tube. If you buy these, lube the edges of the rings to reduce the chance of scratching the tube. The mechanism that attaches the base of the rings to a Weaver-style base don't fit as well as they should...mine didn't have as much purchase on the groove of the base as I would have liked and they canted a bit lower on the right when tightened down. In my opinion, Warne permanent mounts fit better, and I will probably swap these out shortly.
Cons: Fit, weight
This review was written in the old system and had content requirements that are different than reviews written today.