The Kinect system was designed and manufactured to the original specifications set by Magpul Industries for a rail thickness of .080? and .125? thick. The current specifications for M-LOK are a thickness of .080 to .150? as many of the polymer M-LOK products on the market have to be thicker to support glass filled polymer rail systems. Therefore we do not suggest, nor can guarantee our KINECT product will work on these polymer products. Polymer rails can be modified to work, but our Kinect system was intended for use on precision machined aluminum rails within the specification of .080? to .125? overall thickness. With the variable tolerences that polymer parts are capable of, it is not suggested you buy Kinect QD M-LOK mounts unless you are sure the rail is within the specification, or you are able to modify your rail to fit the Kinect system. Measure the thickness of your polymer rails before ordering. The Kinect Pieces are made fully assembled from the factory and not intended to be disassembled by the end user. Because these are mechanical items, all kinect pieces are tested multiple times at the factory to insure they work properly and are securely mounted onto M-LOK rails. So if you see marks of use on your new Kinect piece, do not worry, that is the factory test marks. Since the M-LOK system has varying tolerances, each Kinect piece may attached differently to each different manufacturers rail. (ie: thicker rails, thinner rails, rails of different materials) Kinect was designed to work with the full range of M-LOK accessories on the market..