The intermediate filaments, because they're found outside our cell are also involved in creating structures between different cells so binding cells together. And finally, the microtubule, the thickest and the largest and the strongest type of fiber found in our skeleton. It has a thickness of about 23. It's composed of one type of protein tubulent that comes in two forms. We have alpha and beta tubulin. So basically the alpha and beta globular tubulent proteins create a helical structure that is hollow at the center and that's why we call it a tubule.