My daughter has bruxism i.e. teeth grinding and was waking up with tired, painful and clicking temperomandibular (jaw) joints. I read in the q&a section that these are bpa free. It comes in a set of 4 which consists of 2 big and 2 small ones. My daughter is a tall adult height 14 year old and she used the large. Follow the instructions to mould it to the shape of your teeth. Surprisingly, she sleeps well with it and after 4 nights she says the jaw pain has resolved. Great result I reckon.