Not so great - Seekins Precision MCSRV2 M-Lok Rail System

Purchased this item for an easy replacement as advertised. What a nightmare!! First of all, my carbine is 100% Mil-Spec. Mounted plenty of mil-spec parts on it without a glitch. The rail is well made great quality and finish but it was impossible to put on. The instructions are not clear. So thank God for YOU TUBE videos. Nevertheless, the barrel nut that came with my part was defective. The threads were not machined correctly and you could not torque the barrel nut and as a result the rail could not be mounted.
Barrel shims should have been included but they would spoil the aesthetics of the rail /receiver joint. Too bad since it was really a nice piece. Just returned it to OP.