It is a silicone mold that takes the shape of teeth and is used to relieve teeth grinding (bruxism) during sleep.

How to use: Place in hot water for a few seconds, then apply to the teeth (preferably the lower jaw). Press gently from the edges of the teeth to the tips, and from the front teeth to the back, until it takes the shape.

Wait until it cools down, then it's ready to use each time.