What is it?
This is a set of parts needed to install end-stops on a cheap chinese 'CNC engraver' going by the name of 1610 CNC (sold in Germany via Amazon marketplace under the name of "Beautystar CNC 1610" or some similar names.
What's a 1610 CNC?
There's a couple of cheap "CNC engravers" out there, they usually go by the size of the milling area. In my case it's a "1610" which stands for 160mm x 100mm (XY). These things are quite good for what one could expect from a heap of aluminum extrusions, that is: forget it's a mill, it's a 'carver', if you go easy and slow it can chew through wood (even hardwood) without much struggling. You can get parts with quite accurate dimensions, which means: accurate for wood! 0.05mm (0.002", 2 thou) size accuracy is what we are talking about, which is much less than the wood will expand or contract with humidity. To get even this level of accuracy you have to get the assembly perfect, and this is where it really shows these aren't cnc mills: There are no independent adjustments, there's nowhere to shim spindle, forget tramming, it's all about how good are you with loosening and tightening the right bolts.
Remix from https://www.thingiverse.com/thing:2633933
Modified to support these limit switches...