It seems like they are meant to push your lower jaw forward, but I don't know for sure. If you've never worn retainers, they will definitely affect your speech for a bit and the metal posts would probably get in the way of your tongue. When you order from bracesshop and get your molds, you can ask for a wax plate so you can position your lower jaw where you want to have it when wearing them. (don't do it too much as your jaw really is being pushed forward. I just placed my lower front teeth in line with my uppers)
