Mounted this on an M&P 15-22.
There is no moving compression fitting and the grip was loose on the rail.
To get a tight squeeze fit, I saw cut the kerf (in the center of the rail fitting) down deeper to the top of the handle. Still plenty of material to keep it together, and allowed enough flexibility that the bolt could squeeze the fitting tight against the rail.
Pros: Great value
Cons: Required modification to get a tight fit.
This review was written in the old system and had content requirements that are different than reviews written today.