The Advancement Bars vary in length by 1mm and are designed to hold your lower jaw forwardwhile you sleep. Most individuals will be able to start with Bar 2 or 3. But if you have an over-jetstart with bar 1 or 2. If you have an under-bite, start with bar 4 or 5. If you don’t experience areduction in snoring, move to the next longer bar and try it for a few nights. If you feel too muchforward pressure move the next shorter size. The goal is to find the bar that most comfortablyreduces snoring so you might need to try a few sizes to see what works best for you.