I have Lynx ringmounts on a couple of rifles, and I've been very happy with them. You can get them with flush Allen screws on the clamps, or with levers, rather than thumb screws. They are steel and can be had in gloss blue or matte. I've even used then on a couple of hard kickers, without a drama.
I think they may be sold under the B-square name in the US. This is the Australian website:
http://www.lynxoptics.com.au/ 
