I don't even remember when I designed these. I know I used to keep my printer on a yoga mat so it would make less noise before I did all the silent mods. The printer would sink into the yoga mat, barely letting the bottom fan breathe. Don't really need them anymore, but I still use them.

They are designed to fit into the included rubber feet on the Ender 3 Pro. Since there is only one model, you'll need to mirror two of the feet on the slicer for them to be symmetric.