Be careful when you order is for adults. The mouth guards fit small adults only, but if you are over 5foot 6 and you are of European or Australasian descent then these mouthguards do not go all the way to the back teeth. The advice given to me by this company was to put it in boiling water then stretch it, which is almost the silliest advice I have ever given as the structural integrity would diminish by compromising the wall thickness of the mouth guard. When i mentioned that the mouthguard did not fit the majority of my gym members, I was almost laughed at and told I was fitting it wrong. Ive been doing this for well over 30 years and its me who is "doing it wrong"? I rest my case.