As others have said, it does not come with any directions and I was initially very frustrated. I figured it out after reading previous reviews. 1)Loosen nut 2)tighten screw 3)tighten nut back up. It works great and is a wonderful value. I mounted my Leatherwood Hi-Lux CMR on my BCM upper and it's rock solid.
Pros: Great value for the $
Cons: No directions included
This review was written in the old system and had content requirements that are different than reviews written today.