When I first got the lens stem and put it on my lens I couldn't tighten the knob on the lens enough where the stem wasn't relaxed. I removed the stem from the lens, tightened it a few times and removed it, then put it back on the lens. Now when you tighten it on the lens, it's solid as a rock and doesn't move at all. This is a good lens mount at a much cheaper price than Kirk or RRS lens mounts. I would buy it again if I had to make it over and over again.
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