The only improvement in this improved adjustable Z stop, is that there is a second screw added, making the z-stop more firmly attached to the aluminum 2020 extrusion. Embed the two m3 nuts (one in part A and one in Part B). Attach the limit switch to the bottom piece, attach 1 m3x35mm screw through the top piece, add a spring, then through the bottom piece. Add the other m3x35mm screw from the bottom piece to the top piece (no spring is necessary for this screw). Fasten the top piece to the extruded aluminum frame with 2 M5x12mm screw into the t-slot nuts. The height of the limit switch is adjusted by rotating the screw with the spring.