I made this for some home theater speakers. They have threaded inserts in the bottom of them to receive the carpet spikes but we don't have carpet where these speakers need to live. I did not want to deal with aligning the spikes with their goofy little hard floor pad things so I unthreaded the spikes and made these to thread in instead. I also printed the contact face in several layers of TPU (the black part in the pics) so they are “soft” and have a bit of grip to them. Be advised - if you do this (print TPU as the base layer) you better get a crowbar to get them off. I did this on my satin print board and good grief, they stick! So put some glue stick down or something for a release agent first if you do the TPU thing. I printed the rest of these (the white portion in the pics) in PETG. FreeCAD file is included here so you can tweak things as you need.