Small size Deluxe Outlined on the foldout (included in package) are personal fitting instructions. They are easy to follow and take only a few minutes using hot water and can be done in the privacy of your home This product is NOT a partial denture or a “DENTAL DEVICE” and is intended for temporary use only For aesthetic purposes only. Do NOT eat or sleep while using this product. It is difficult to determine the appropriate size of the Instant Smile teeth for a particular person’s mouth. Based on the feedback we’ve received from other buyers, the SMALL size would typically fit a child’s mouth or a small adult mouth. The MEDIUM are actually now labeled “One Size Fits All” and fit an average adult’s mouth. This is a general guideline and is not a guarantee. We are unable to accept returns on used Instant Smile teeth. Please inspect the teeth to determine if they will fit prior to use.