If quality of design, construction and functionality is important to you, even in tube rings, you might want to consider the Japanese K-Astec range.
Mine for the FSQ-106ED arrived this morning. I have since fitted them and did a little commentary on CN about them:
http://www.cloudynights.com/topic/50.../#entry6669125
Sure, not cheap at DOUBLE the price of Parallax rings, but their quality speaks for themselves, and it includes the top plate. The fit to the tube is EXACTING (uses thin felt). I MUCH prefer split rings to hinging ones.
Ignore my scarred up Vixen dovetail - ordered a new one today
Will put some brass plates on it this time around.