This is a container made of three stacked nuts. It could be used as a pencil holder or a tool holder. It could even be used to hold your nuts. The smaller one in the photo was scaled to 55.55% and is used as a toothpick holder.
There are three variations:
1) a thin walled container that has the most room for containing things. The hole is approximately 34 cm²
2) a thick walled container that has more realistic dimensions for the nuts. The hole is approximately 22 cm²
3) a threaded container that has the most realistic nuts. The hole is approximately 20 cm²
I also included an STL with all 3 variations so that you can easily compare all 3 side by side.
I got the idea from Nut Pen Holder. I wanted to print it, but it's non-manifold with 470,495 errors and none of the three different slicers that I use could slice the model properly. So I created my own models using slightly modified variations of the nuts from metric iso screw & nut. I prefer my thin-walled version anyway since there's more room in it, it uses less material to make, and there are no threads to collect dust.