A few days ago I ordered this Mouthguard for my Wing Chun training. As described in the instructions, I put the mouthguard for 30 seconds in boiling water, 1 Second cooled him and then stuck it in his mouth. When removing from the water, I noticed already on that mouth guard was torn up and down incisors by the heat in the mouth, this was no longer forms cleverness. So of course this is useless! Absolutely failed.