I created these to help me hold the nuts on the back side of my Anet A8 when I had to adjusted the z axis limit switch. Works really great and for beeing my first "useful" design I'm pretty happy.
Let's hold those nuts! ;)
(Planing on adding M2, M8 & M10 in the near future)
I'm not sure what infill I used, but somewhere around 20% should be enough.