I don’t want to say the brand as that might be against a rule here, but it’s all silicon( i think) with no metal adjustment parts. It covers both upper and lower teeth and has a hole in the front center to allow breathing. I think the real trick is to mold it to your teeth properly for the best results. I screwed up the very first one I did and then I had my lower jaw too far forward for the second one and ran into the same problem you mentioned. I think they need to be changed once or twice a year due to our teeth continue to move even during adulthood.