These are actually very good quality with solid lockup mechanisms. Takes a little fine tuning to get it just right but once you do, its solid with no movement on the rail. Cant yet speak to repeatability as I have not yet shot with it yet but looks like it will be consistent.
Pros: removable, low cost
Cons: Not made in US
This review was written in the old system and had content requirements that are different than reviews written today.