I ordered two packages of these rings. Only one ring in each packsge was usable. The screws holes for one ring of each package would not line up (top ring versus bottom ring) once the screws were removed. The screw holes in the upper ring in both cases were too wide to match the bottom holes. The screws were difficult to remove and could not be replaced. Poor quality control!
Cons: screw holes don't line up.
This review was written in the old system and had content requirements that are different than reviews written today.