Designed for the microswitch mechanical endstop. If you are using Aluminum Couplers on your Z-Axis, I'm not totally certain if it will not rub the side of your coupler. I did try to make the endstop holder as thin as possible.
What I used:
3 - M3x20mm & 1 - M3x15 bolts plus washers and nuts. 1 spring inside of a retractable pen that I cut in half. 2 - M2x12mm & Nuts for Micro Mechanical Endstop.
Printed this at 0.2mm layer height with 45% infill. Also with .35 nozzle. It's favorable to use ABS but PLA will work too.
Added 10mm smooth rod holder.