Here is a couple of pictures of modern thread guides. There are many manufacturers of these mostly from China and foreign countries. They are made of plastic, metal, ceramic and a product called alumina which is some alloy made with aluminum and ceramic for durability. The pieces I have though are older styles and not of the modern manufacture. They are pretty neat, although not insulator related use but to shed light on what some people are calling insulators. Some could be used that way but are inded textile thread guides.