Summary this is a Z stop adjuster for the Max Micron Prusa i3 Clone and other 20mm aluminum extruded framed printers. Works well, actually better than planned You'll need one of the extra M5 screws and the twist mount thing to hold to frame. you'll also need a M4 round head and nut. Please Note - 1 - you do NEED to lightly file/sand the joint, it's a tad tight on purpose as you want it to move freely but not bobble and everyone's printers are lightly different so depending on your print it will vary how much sanding or filing (I highly recommend getting files, so much better for this purpose than sand paper) Be careful NOT to file or sand the lip off inside the arm, this holds it in place! 2 - Crazy glue the cap and the little nut in place so they stay and don't shift. 3 - suggest printing at 0.1 or higher layer resolution for best results and fit.