Wanhao i3 clamping adjustable z endstop

You need:

4x M3x14 (or longer)
1x M3x35 (or M3x40, does not need to be fully threaded; adjust longer for a longer spring so it just protrudes from its trap nut as the spring begins being compressed)
5x M3 hex nuts
1x retractable pen spring (approx 4.2mm OD, 0.4mm wire, 20-25mm long)
1x printed parts
2x M2 screws that came on the endstop