I saw some types of these under the Leonardo D. engerneering(I think, something like that,motion.somethen ) mustseeum in milan years ago,so awesome. great way to control back lash and thrust at the same time and adjustable too. I saw oh somuch in that dirt floor machine shop with 4 story mustseeum built over it. I even learned how DOM is made there....I had no idea, and no idea that stuff was going on centurys ago.I need to go back for another look for a few years.