Terrible. When tightened on the base, they bend inward, due to their design, which requires bending to fully tighten. Then, if you later take them off, they are so bent, they will not slide onto a weaver or P rail. Trying to bend them back, and they break - yes it happened. Big boo to Zee rings. I used to sing their praises; not anymore. Leupold or Warne for me, most of the time. Or Talley. Even Weavers, though ugly, are better than these. Only thing worse, not counting B-square, are Millett "Angle-Loc" rings - I despise them with a passion. YMMV. Discuss.