Here are some pictures of my 4 Mexican fence post whatever they are. Yes, I got them from Jack and yes, I am totally delighted with them. I doubt they are insulators but they are very nicely made and decorative, I have no idea what they were used for and these ones don't seem to have been used at all. The 'pinhole' inside is shaped rather than cylindrical. They are all slightly different, one is frosted. The pictures don't do them justice though, the green and the dark blue are lovely in the light.