These are 1 ½ diameter leveling feet that use a 5/16-18 carriage bolt. The lower and top clip together with the help of a hammer. There is also an optional tpu pad that can be glued to the bottom.
Recommend printing the lower part with 13 bottom layers at 0.20mm layer heigh. This will give a sold base under the bolt. I printed mine out of petg, but pla will work just as well.
The author marked this model as their own original creation.