Pos china junk - AIM Sports Inc Mid-Length AR Free Float Quad Rail Mount

Threads are soo loose (NOT Matched) that the rail will skip over a thread or two when rail is bumped sideways. 0.019" difference between male and female OD vs. ID at the barrel nut rail engagement. China wants you to have inferior equipment, intentionally built this way to render your weapon inoperable during a real fire fight.