They use Megawhite which is Chlorine Dioxide. Legally they arent allowed to advise or administer this as they arent dental practitioners, which is why they dont explain it or carefully apply this. You are effectively given an “at home” kit to use in their office. Dont waste your money. Go somewhere that uses 6% hydrogen peroxide that will give you an actual difference, and safely too. Google Megawhite and Chlorine Dioxide.